JPH0794378A - Method of electron beam exposure - Google Patents

Abstract

PURPOSE:To form an accurate pattern on non-uniform base by electron beam exposure that is based on an appropriate proximity effect corrective quantity obtained for each of the patterns specified by corrected exposure pattern data and uncorrected exposure data. CONSTITUTION:Pattern data (w) to be corrected is obtained in consideration of the mass number or reflectivity of a layer under a sample surface. The pattern data is ANDed with exposure pattern data (g) to obtain corrected pattern data A, B and C. Then, the pattern data A, B and C are removed from the exposure pattern data (g) to obtain uncorrected exposure data E, F and G. An appropriate proximity effect corrective quantity is determined for each pattern that is specified by the corrected exposure pattern data A, B and C and the uncorrected exposure data E, F and G. Electron beam exposure is performed according to the corrective quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam exposure method, and more particularly to a method for correcting a so-called proximity effect to form a highly accurate electron beam exposure pattern.

[0002]

2. Description of the Related Art In pattern formation in an electron beam exposure method, electrons which have entered a resist film are subjected to multiple scattering by the resist to spread and spread, and backscatter by electrons which are reflected by the substrate and re-enter the resist film are desired. The phenomenon that the pattern is drawn larger than the pattern size occurs. This phenomenon is prominent when the patterns are densely present, and is called a proximity effect.

[0003] absorbed energy intensity in the resist film due to the incident electron F (r) is the table in F (r) = exp (-r 2 / A 2) + B · exp (-r 2 / C 2) ( Equation 1) To be done. Where r is the distance from the electron incident point,
A, B, and C are constants, and the first term on the right side is the forward scattering and the second term.
The terms are those given by backscattering.

As a proximity effect correction method for correcting the proximity effect in advance to obtain a pattern as designed, a figure deletion method, an exposure amount correction method, a combination method of both methods, and a ghost exposure method are known.

The figure deleting method is a method of exposing a pattern by correcting the exposure pattern to be smaller than a desired pattern in consideration of the spread of the pattern width after the exposure. The exposure amount correction method is a method of calculating an electron beam irradiation amount so as to obtain a pattern dimension as designed and performing exposure based on the calculated irradiation amount. The ghost exposure method is a method in which a desired pattern is exposed and then a black-and-white inverted pattern is overlapped and exposed to cancel the influence of backscattering.

[0006]

The above-described proximity effect correction method is premised on that the substrate on which the pattern is to be drawn is made of a uniform material and the resist film is also uniform in thickness. However, on an actual substrate, various thin films (for example, SiO ₂ , Si _{3) are} subjected to various semiconductor processes.
A pattern of N ₄ , aluminum, titanium, tungsten, etc.) is formed, and the material is not uniform.

When patterning is performed on such a substrate, the backscattering intensity from the substrate becomes nonuniform depending on the location. Therefore, there is a problem that even if the proximity effect is properly corrected in a certain place, it is not properly corrected in another place. In particular, the backscattering intensity becomes extremely large in the portion where the heavy metal film such as the tungsten wiring is formed,
There is a problem in that the proximity effect cannot be properly corrected only in this portion, resulting in defective resolution.

With reference to FIGS. 3A to 3F, problems in forming a pattern in the portion where the heavy metal film is formed will be described in detail. FIG. 3A is a plan view of the heavy metal film 51 formed on the substrate 50, and FIG. 3B is XX ′.
It is sectional drawing of a direction. FIG. 3C is a plan view of an upper layer pattern formed on the surface of the substrate 50 on which the heavy metal film 51 is partially formed. Two linear patterns 56a and 56b having the same width are formed, and the pattern 56
A part of a overlaps the heavy metal film 51.

FIG. 3D shows the substrate 50 and the heavy metal film 51.
FIG. 9 is a cross-sectional view in the XX ′ direction when an upper layer film 52 and a negative resist film 53 are formed on the surface. Patterns 56a, 56b
The electron beam 55 is irradiated only to the portion. Of the resist film 53, a portion 54a irradiated with the electron beam 55,
54b is altered. Altered portion 5 corresponding to pattern 56a
4a is also exposed by the electrons backscattered by the lower heavy metal film 51. Therefore, the line width of the altered portion 54a is wider than the line width of the pattern 56a.

FIG. 3 (E) is a plan view of the substrate when the unexposed portion of the resist film 53 is removed and the upper layer film 52 is selectively etched. FIG. 3 (F) is a cross section in the XX 'direction. It is a figure. Upper film patterns 52a and 52b are formed corresponding to the patterns 56a and 56b. Pattern 5
2b has the line width as designed because the proximity effect is properly corrected, but the portion of the pattern 52a that overlaps with the heavy metal film 51 is not properly corrected for the proximity effect, and thus the line width is backscattered. The breadth widens.

As described above, when the material of the underlayer is not uniform, the influence of backscattering is not uniform, so that it is difficult to obtain a pattern as designed by the conventional proximity effect correction method.

It is an object of the present invention to provide an electron beam exposure method capable of forming a pattern with high accuracy even when the material of the base is not uniform.

[0013]

In order to facilitate understanding, the following description will be given, by way of example only, with reference numerals in FIG.

The electron beam exposure method of the present invention is an electron beam exposure method in which an electron beam is directly drawn on a resist film formed on the surface of a sample based on pattern data created in advance. In consideration of the mass number or reflectance of the layer, the step of obtaining the compensation target pattern data (w) and the logical product of the exposure pattern data (g) designating the exposure pattern and the compensation target pattern data (w) are calculated. , A step of obtaining compensation exposure pattern data (A, B, C), and removing the compensation exposure pattern data (A, B, C) from the exposure pattern data (g) to obtain non-compensation exposure pattern data (D, E). , F) and for each pattern designated by the compensation exposure pattern data (A, B, C) and the non-compensation exposure pattern data (D, E, F). A proximity effect correction amount calculating step of calculating a proximity effect correction amount, and a step of performing electron beam exposure based on the proximity effect correction amount.

In the proximity effect correction amount calculation step, based on the intensity distribution of the exposure beam based on the mass number or reflectance,
It may include a step of correcting the pattern size and the exposure amount. .

[0016]

It is possible to obtain the pattern data of the area for which the proximity effect correction amount needs to be compensated by calculating the logical sum of the pattern data of the layers formed of the material for which the proximity effect correction amount needs to be compensated. it can. By calculating the logical product of the pattern data of the area for which the proximity effect correction amount needs to be compensated and the pattern data of the area to be exposed, the proximity effect correction amount is compensated to obtain the pattern data of the area to be exposed. be able to.

By compensating the proximity effect correction amount from the pattern data of the region to be exposed and removing the pattern data of the region to be exposed, it is possible to obtain the pattern data of the region to be exposed with the usual proximity effect correction amount. it can.

By calculating the proximity effect correction amount for each of the above regions, an appropriate correction amount can be calculated regardless of the material of the underlying surface of the exposed surface. Therefore, it is possible to form a pattern with high accuracy even when the underlying material of the exposed surface is not a uniform material.

[0019]

EXAMPLE An example of the present invention will be described by taking the case of forming a bipolar transistor on a silicon substrate as an example.

FIG. 1A shows a sectional view of an example of a bipolar transistor. LOCO on the surface of the silicon substrate 10
Field oxide film 11 and polysilicon layer 1 by S technology
2, an insulating film 13, a polysilicon layer 14, a tungsten layer 15, an insulating film 16, a tungsten layer 17, and an aluminum layer 18 are patterned and laminated in a predetermined pattern.

FIG. 1B shows a plan view of the pattern of each layer mask. The pattern a is the field oxide film 11, the patterns b and c are the polysilicon layer 12, the pattern d is the insulating film 13, the pattern e is the polysilicon layer 14, and the pattern f.
Is for insulating film 16 and pattern g is for patterning aluminum layer 18. Tungsten layer 15,
No. 17 does not use a mask pattern because it selectively grows on the surface of the polysilicon layer.

When each layer is formed using the above mask pattern, tungsten is formed in the region defined by the patterns d, e and f. That is,
Area w designated by the pattern data obtained by calculating the logical sum of the pattern data representing the patterns d, e, and f
A tungsten layer is formed on. Region w is shown in FIG.
It is indicated by the diagonal line in (B).

A process of forming the aluminum layer 18 on the insulating film 16 and the tungsten layer 17 formed in the opening will be described. A resist film is applied to the surface of the aluminum layer deposited on the entire surface of the substrate, and the resist film is exposed along the pattern g.

When electron beam exposure is performed along the pattern g, the influence of backscattering differs between the region w in which tungsten is formed as the base and other regions. Figure 1
(C) shows a pattern obtained by dividing the pattern g into a region w affected by backscattering by the tungsten layer and a region not affected by backscattering. Region w having a tungsten layer as a base
Pattern data w, that is, pattern data d, e,
The logical product of the logical sum of f and the pattern data g is calculated. Regions A, B, and C corresponding to this logical product are regions affected by backscattering by the tungsten layer. Areas D, E, F excluding the areas A, B, C from the pattern g
Is a region that is not affected by backscattering by the tungsten layer.

In this way, the pattern g can be divided into the regions A, B and C affected by the underlying tungsten layer and the regions D, E and F not affected. The proximity effect correction corresponding to the material of the base is performed for each of the patterns A to F.

FIG. 2 shows a double Gaussian intensity curve. The horizontal axis represents the distance from the center of the pattern, and the vertical axis represents the exposure intensity.
Curves α and β respectively correspond to the material of the base and show the exposure intensity that can be approximated by two Gaussian distributions.

A material code representing the material of the base is associated with each of the divided patterns A to F. Next, based on the double Gaussian intensity curve corresponding to each material code, pattern size correction and exposure amount correction are performed for each of the divided patterns A to F. When the underlying layer has a tungsten layer, the effective exposure dose varies depending on the pattern size, but varies by about 15 to 20%.

As described above, the pattern to be exposed is divided according to the material of the base, and the pattern size correction and the exposure amount correction are performed for each of the divided patterns, so that the appropriate proximity effect correction corresponding to the material of the base is performed. It can be performed. Therefore, the pattern as designed can be formed with high accuracy.

In the above embodiment, the exposure pattern is divided into two types depending on whether or not the underlying material has a tungsten layer. However, the other materials are also divided into three or more types. Good. Further, considering the depth from the surface of the resist film to the underlying heavy metal film, the exposure pattern may be divided according to the difference in depth. As a result, the influence of backscattering due to the difference in depth can be compensated for, and a more accurate pattern can be formed.

Although an example of performing the pattern dimension correction and the exposure amount correction based on the double Gaussian intensity curve corresponding to each material code has been described, other criteria such as a triple Gaussian intensity curve may be used.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0032]

According to the present invention, even if the material of the underlayer on the surface to be subjected to electron beam exposure is not uniform, the proximity effect correction corresponding to each material can be performed. Therefore, it becomes possible to form a high-definition pattern on the surface of which the material of the base is different.

[Brief description of drawings]

FIG. 1 is a sectional view of a pattern-formed substrate according to an embodiment of the present invention, a plan view, and an exposure pattern divided according to a material of a base.

FIG. 2 is a double Gaussian intensity curve used in the examples of the present invention.

3A and 3B are a plan view and a cross-sectional view of a pattern formation substrate for explaining a proximity effect of electron beam exposure according to a conventional example.

[Explanation of symbols]

 10 Silicon substrate 11 Field oxide film 12, 14 Polysilicon layer 13, 16 Insulating film 15, 17 Tungsten layer 18 Aluminum layer 50 Substrate 51 Heavy metal film 52, 52a, 52b Upper layer film 53 Resist film 54a, 54b Altered part 55 Electron beam 56a , 56b Upper layer pattern

Claims (2)

[Claims] 1. An electron beam exposure method in which an electron beam is directly drawn on a resist film formed on the surface of a sample based on previously created pattern data, and the mass number or reflectance of a layer formed below the surface of the sample. In consideration of the above, the step of obtaining the compensation target pattern data (w), and the logical product of the exposure pattern data (g) designating the exposure pattern and the compensation target pattern data (w) are calculated,
Obtaining compensated exposure pattern data (A, B, C); removing the compensated exposure pattern data (A, B, C) from the exposure pattern data (g) to obtain non-compensated exposure pattern data (D, E, F), and a proximity for obtaining an appropriate proximity effect correction amount for each pattern specified by the compensation exposure pattern data (A, B, C) and the non-compensation exposure pattern data (D, E, F). An electron beam exposure method comprising: an effect correction amount calculation step; and a step of performing electron beam exposure based on the proximity effect correction amount. 2. The electron beam exposure according to claim 1, wherein the proximity effect correction amount calculation step includes a step of correcting the pattern size and the exposure amount based on the intensity distribution of the exposure beam based on the mass number or the reflectance. Method.