JP2001076999A - Electron drawing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for idenpendently correcting in-graphic proximity effect in each partial end batch shot region, while using a conventional device at electron drawing for executing exposure by partial end batch shot. SOLUTION: This electron drawing is performed by using a partial end batch plotting method through the use of the repeated units of contact patterns 11 as main patterns. When a direction in which the other proximate contact patterns 11 are not present exists in the surrounding of the contact patterns 11 in a partial end batch shot region 13, auxiliary patterns 12 derived through the use of an EID(exposer intensity distribution) function for correcting an in-graphic proximity effect is auxiliarily exposed, so as to be overlapped on the partial end batch shot region 13 by the partial end batch plotting method or a variable molding rectangular method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electron beam lithography method, and more particularly to an electron beam lithography method for performing electron beam lithography in an LSI manufacturing process.

[0002]

2. Description of the Related Art FIG. 6 shows an example of an overall configuration diagram of an electron beam drawing apparatus and system used for lithography of a capacitor contact and the like in a DRAM manufacturing process. As shown in FIG. 6, the electron beam lithography apparatus main body 100 has a first aperture 61 provided with a rectangular hole and a second aperture 52 provided with several types of opening patterns such as rectangles and LSI pattern shapes. And are provided. And the electron gun 62
The electron beam 63 emitted from the first aperture 6
1 and is deflected by a forming lens 64 and a forming deflector 65 to irradiate an appropriate opening pattern in the second aperture 52. The electron beam 63 that has passed through the second aperture 52 is reduced and projected to a desired position on the sample 14 via a reduction lens 66, a positioning deflector 67, and an objective lens 68. In this case, the second aperture 52
Are drawn by one exposure.

The operation of the electron beam lithography apparatus main body 100 is as follows.
It is defined and controlled by the electron beam drawing system 200. That is, in the electron beam writing system 200, C
The LSI is designed by the AD system 71, and the data such as the contact pattern in the memory cell array is sent to the data processing computer 72 and stored as design data. In addition, creation of design data of an auxiliary pattern described later is also performed by the data processing computer 72. afterwards,
The design data is sent to the control computer 73 and converted into EB data format. Next, the data is sent to the control interface 74, based on which the acceleration voltage, blanking, deflection electrode,
Control of the sample stage and the like is performed. Note that a partial collective mask described later is manufactured based on the above design data and installed in the second aperture.

An electron beam writing method using such an apparatus and system is a method of directly generating a pattern from data under computer control and writing the pattern on a sample. As a lithography technique utilizing this, there are a variable-shaped rectangular drawing method, a batch drawing method, and the like. The variable shaped rectangle drawing method selects a rectangular hole as the second aperture in the above-described apparatus,
This is a method in which a rectangular pattern of an arbitrary size can be drawn on a sample by combining with a first aperture provided with a rectangular hole, and the size can be changed even during drawing.
However, in this method, even when there is a continuation of the same pattern such as a contact of a memory LSI cell such as a DRAM, a very large number of drawing times and drawing times are required since the method is individually divided into rectangles and handled. It will take.

Therefore, when the same pattern is continuously drawn, a partial batch writing method for simultaneously writing a plurality of patterns on a sample using a partial batch mask provided with a plurality of the same patterns as a second aperture is usually used. Is used. That is, a pattern formed in the second aperture is drawn on a wafer by passing an electron beam through a first aperture provided with a rectangular hole and a second aperture having a plurality of same pattern openings. It is possible to drastically reduce the writing time of a pattern having a characteristic. The drawing of the pattern is called a partial batch shot. At this time, since the partial batch shot is drawn at a time using the partial batch mask, the whole of the partial batch shot area is drawn with the same electron beam irradiation amount.

When the exposure method using an electron beam is used as described above, a proximity effect such as distortion of the shape of an adjacent pattern due to a change in an exposure amount due to scattering of the electron beam in front of or behind an object to be irradiated may occur. Are known. FIGS. 7A and 7B are diagrams for explaining the proximity effect. FIG. 7A shows a proximity effect in a figure that causes a shape distortion in a single figure. This is due to the spread of forward scattering of the electron beam. The proximity effect in the figure is caused by an insufficient amount of exposure around the figure. (B) The effect. (C) shows the exposure amount on the s-line in (b). FIG. 7A shows an inter-graphic proximity effect in which a pattern of an adjacent graphic contacts. This is due to the spread of the backscattering of the electron beam, and the inter-graphic proximity effect is an effect (b) in which a part or the whole of the portion where the exposure pattern of the adjacent graphic (a) is in close proximity. Again, in this case,
(C) shows the exposure amount on the s-line in (b). Note that FIG.
As the proximity condition in (a), a range of about 10 μm or less is assumed.

For this proximity effect, various correction methods have been proposed and put into practical use. Above all, a pattern in which the exposure area and the non-exposure area are inverted over the normal exposure,
A ghost method in which exposure is performed in a blurred state in which a focal position of a lens is removed from a substrate is widely used. By using this correction method, the exposure amounts can be made uniform using the fact that they have complementary characteristics, and the influence of the proximity effect can be substantially canceled. When this ghost method is performed, the overall exposure level increases, but the deformation of the exposure pattern due to the approximate proximity effect is corrected.

When a partial batch writing method for a contact pattern or the like of a memory cell array is performed by employing the above correction method, a pattern (one or a plurality of contact patterns) of a repeating unit is first extracted from design data. Thereafter, using the pattern of the repeating unit as a main pattern, a partial collective mask having an opening in which the shape of the pattern is uniformly enlarged is prepared and set as a second aperture. At the same time, the design data is
The format is converted to B data. Further, an auxiliary pattern for the proximity effect is created by the ghost method, and the design data is derived. This design data is format-converted into EB data for variable-shaped rectangle drawing so that variable-shaped rectangle drawing can be performed for each partial batch shot area or a unit of a larger scale. After that, the obtained EB
The main body of the electron beam device is controlled based on the data, and the whole surface of the memory cell is drawn. In the above-described drawing of the normal auxiliary pattern, a method of using a variable shaping rectangular method while modulating the electron beam irradiation amount by each area is performed for each area of a partial batch shot area of about 5 μm square.
Therefore, auxiliary exposure is performed in the one-shot area with the same irradiation amount. Exposure for correction may be performed before or after exposure of the main pattern.

However, even after the correction as described above, attention is focused on, for example, a partial batch shot area at the upper right end of the memory cell array 10 formed on the sample, as shown in FIG. 8, for example. Another contact pattern 1 close to the periphery of a certain contact pattern 11
If there is a direction in which 1 does not exist, the exposure amount of the contact pattern 11 is insufficient due to the proximity effect in the figure, and a drawing failure such as the thinning of the pattern 81 is caused.

[0010]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art.
The purpose is that, when drawing using the partial batch writing method while using the conventional apparatus, each partial batch shot area is independently drawn with the drawing intensity due to the intra-graphic proximity effect in the partial batch shot area that is a minute part. It is an object of the present invention to provide a method for more accurately and efficiently correcting the gradient of an object, thereby improving the dimensional accuracy in the entire array surface and in the partial collective shot area in the partial collective writing method. is there.

[0011]

According to the present invention, there is provided, according to the present invention, (1) a main exposure step of exposing an array region having a repetitive pattern by a partial batch shot of a main pattern; An auxiliary exposure step of exposing a partial batch shot area that needs to correct the proximity effect using an auxiliary pattern for correction, comprising: an electron beam drawing method, wherein the auxiliary pattern for correction and its exposure time are: An electron beam writing method is provided, which is determined based on a simulation result of exposure of a main pattern and exposure of an auxiliary pattern. And, preferably,
The exposure in the step (2) is performed using a partial batch mask or a variable rectangular shaping pattern with or without a metal mesh in the opening. Also, preferably,
It is provided that the simulation is performed using an EID function, and is performed only on the outermost partial batch shot area of the array area.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. [First Embodiment] A first embodiment of the present invention will be described with reference to DR.
The lithography of the capacitance contact in the AM manufacturing process will be described as an example. An overall configuration diagram of an example of an electron beam drawing apparatus and system used in the present embodiment is the same as the apparatus and system in the conventional example shown in FIG. 6, and their functions are also the same as those in the conventional example. However, the second aperture 52 is configured so that any of a rectangular hole for variable-shaped rectangular drawing and a partial collective mask for partial collective drawing can be installed. FIG. 1 is a plan view showing an end of a memory cell array 10 on a sample according to an embodiment of the present invention. Reference numeral 11 denotes a contact pattern which is a pattern of a unit of repetition, 12 denotes an auxiliary pattern for correction, and 13 denotes a partial collective shot area. As shown in FIG. 1, the contact patterns 11 are regularly arranged by array development. As described later, in the present embodiment, the auxiliary pattern 12 is realized by a variable shaped rectangle.

FIG. 2 is a flowchart showing this embodiment. A pattern in a unit of repetition is extracted from the design data of the contact pattern and is set as a main pattern. Based on this, a partial collective mask for a main pattern capable of simultaneously exposing a plurality of contact patterns is manufactured and installed in the second aperture. Then, when a certain partial batch shot area (usually the endmost area in the array) is selected and there is another contact pattern close to the entire periphery of all the contact patterns in that area, only the main pattern is left as it is. Output the design data of However, when there is a contact pattern in which no other contact pattern exists close to the entire periphery in the partial batch shot area, an auxiliary pattern for a variable shaped rectangle is created in addition to the main pattern. . Thereafter, the proximity effect in the figure is corrected by performing auxiliary exposure (variable rectangular auxiliary pattern exposure) based on the auxiliary pattern for the variable shaped rectangle. Then, design data of the main pattern and the auxiliary pattern for the variable shaped rectangle is output. This is similarly examined for all partial batch shot areas. Next, after format conversion of the design data into EB data for variable-shaped rectangular drawing and partial collective drawing, partial collective drawing of the main pattern is performed on the entire array pattern by using them, and then the pattern is overlaid on the partial collective shot area. To draw a variable-shaped rectangular auxiliary pattern. Finally, the correction of the proximity effect by the ghost method or the like is carried out for the purpose of avoiding the inter-graphic proximity effect as in the past.
In addition, the pattern close to the above assumes that the distance between the patterns on the sample is 10 μm or less.

The above-mentioned auxiliary pattern is created as follows. The spatial distribution of the electron absorption energy density in the sample is EID (Exposure Intensity Distribution)
And the EID function in the function display is 2
It is known from experience that it can be adequately represented by a combination of Gaussian distributions with two different variances. _{f p (r) = (c} 1 / β f 2) exp (-r 2 / β f 2) + (c 2 / β b 2) exp (-r 2 / β b 2) In the equation, beta _f , Β _b are quantities representing the spread of forward scattering and back scattering of electrons incident on the sample, respectively, c ₁ , c ₂
Is a constant, r is the distance from the electron, and f _p (r) represents the amount of energy stored at the distance r.

In the data processing computer 72 of the electron beam lithography system shown in FIG. 1, the absorption energy density at the time of main pattern exposure is obtained in advance for each partial batch shot area by numerical analysis such as Monte Carlo simulation, and the result is obtained by the EID function. And perform a comprehensive simulation under actual exposure conditions. Based on experience, we first assume the shape and exposure time of the auxiliary pattern so that independent correction can be performed to some extent in each partial batch shot area by exposure, and in each partial batch shot area when drawing using it. The exposure amount distribution is simulated, and based on the result, the shape of the auxiliary pattern and / or the shape in which the exposure time is changed and the proximity effect in the figure is appropriately corrected based on experience. By repeating this process, the shape of the auxiliary pattern that can correct the proximity effect in the figure appropriately for each partial batch shot area is determined (the step of “creating the auxiliary pattern” shown in FIG. Process). Here, the opening area of the auxiliary pattern is not limited to the opening area of the main pattern, but can be set arbitrarily within the corresponding partial batch shot area. Finally, as shown in FIG. 3, the auxiliary pattern is divided into rectangles so as to be able to be exposed by the variable-shaped rectangle method, thereby forming auxiliary patterns for the variable-shaped rectangle. FIG. 3 is an explanatory view of the state of the end portion of the memory cell array 30 after the auxiliary exposure. In FIG. 3, reference numeral 31 denotes a variable rectangular auxiliary pattern of the auxiliary exposure, and 32 denotes a partial collective shot area. When determining the shape of the auxiliary pattern, the exposure time may be optimally set for each rectangular auxiliary pattern, assuming the shape of the rectangular auxiliary pattern from the beginning.

The auxiliary pattern 12 initially given as a hypothesis is, for example, a key-shaped auxiliary pattern 12 along the outermost end of the contact pattern 11 in the partial batch shot area 13 as shown in FIG. And linear type are selected by experience. Note that the order of all the above exposures can be changed.

[Second Embodiment] Next, a second embodiment of the present invention will be described.
An embodiment will be described. This embodiment is also DRA
M relates to lithography of a capacity contact in a manufacturing process of M. The overall configuration of an example of the electron beam drawing apparatus and system used in the present embodiment is the same as the apparatus and system shown in FIG. 6, and their functions are also the same as those of the conventional example. However, in the present embodiment, since the correction is performed by a partial batch shot, the electron beam drawing apparatus
The second aperture 52 is configured so that a plurality of partial batch masks for partial batch writing can be provided. The condition of the contact pattern in the present embodiment is also the first.
The embodiment is the same as that shown in FIG. FIG. 4 is a flowchart illustrating the present embodiment. The flow of the present embodiment is performed in the same manner as in the first embodiment up to the step of “creating an auxiliary pattern”. After the creation of the auxiliary pattern, a partial collective mask for the auxiliary pattern is manufactured and set on the second aperture. Subsequent steps are the same as in the first embodiment.

FIG. 5 is a plan view showing a part of the auxiliary pattern partial collective mask obtained in the above-described flow. The auxiliary aperture 52 is provided in the second auxiliary exposure aperture 52. A plurality of partial batch masks 51 are formed. Then, based on the EB data obtained from the auxiliary pattern, the auxiliary exposure is performed by using the second aperture for auxiliary exposure mounted on the electron beam writing apparatus so as to overlap the partial outermost shot of the memory cell array. The auxiliary pattern opening 53 may be an opening having a metal mesh.

Normally, the exposure amount in which a defective drawing portion such as a pattern thinning due to the proximity effect in a figure is insufficient is almost uniform, and is almost completely eliminated by a single correction. If it is larger, another auxiliary pattern may be additionally created until it is eliminated, a partial collective mask based on the auxiliary pattern may be created, and multiple exposure may be repeated.

[0020]

As described above, the electron beam lithography method of the present invention provides an auxiliary pattern for correcting the proximity effect in a figure obtained by a simulation result before and after partial batch writing of a main pattern. Therefore, the drawing intensity distribution in the partial batch shot area can be independently made uniform using a generally used apparatus. Therefore, according to the present invention, the drawing intensity can be made uniform in all the partial collective shot areas such as the memory cell array, and the processing dimensions in all the partial collective shot areas can be made uniform with high accuracy. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a plan view of a memory cell array for describing an embodiment of the present invention.

FIG. 2 is a flowchart showing a first embodiment of the present invention.

FIG. 3 is a plan view of a memory cell array for explaining the first embodiment of the present invention.

FIG. 4 is a flowchart showing a second embodiment of the present invention.

FIG. 5 is a plan view of a second aperture for describing a second embodiment of the present invention.

FIG. 6 is an overall configuration diagram of an electron beam drawing apparatus and an electron beam drawing system used in the conventional example and the present invention.

FIG. 7 is a diagram (part 1) for describing a conventional partial batch drawing method.

FIG. 8 is a view for explaining a conventional partial batch writing method (part 2).

[Explanation of symbols]

 Reference Signs List 10 memory cell array 11 contact pattern 12 auxiliary pattern 13 partial batch shot area 14 sample 30 memory cell array 31 variable rectangular auxiliary pattern 32 partial batch shot area 51 partial batch mask 52 second aperture 53 auxiliary pattern opening 61 first aperture 62 electron gun 63 Electron beam 64 Molding lens 65 Molding deflector 66 Reduction lens 67 Positioning deflector 68 Objective lens 71 CAD system 72 Data processing computer 73 Control computer 74 Control interface 81 Pattern thinning 100 Electron beam writing apparatus main body 200 Electron beam writing system

Claims (7)

[Claims] 1. A process of exposing an array region having a repeated pattern by repeating a partial batch shot of a main pattern; and (2) correcting a partial batch shot region in which a proximity effect needs to be corrected. In the electron beam lithography method in which the step of exposing using the auxiliary pattern for exposure is performed in this order or the order is changed, wherein the auxiliary pattern for correction and the exposure time thereof are different between the exposure of the main pattern and the exposure of the auxiliary pattern. An electron beam drawing method characterized by being determined based on a simulation result. 2. The electron beam lithography method according to claim 1, wherein the exposure in the step (2) is performed using a partial batch mask or a variable rectangular shaping pattern. 3. The electron beam lithography method according to claim 2, wherein a metal mesh is provided in an opening of the partial batch mask used for the exposure in the step (2). 4. The simulation according to claim 1, wherein the simulation is an EID (Exposu).
4. An electron beam drawing method according to claim 1, wherein the method is performed using a re-intensity distribution function. 5. The electron beam lithography according to claim 1, wherein the exposure in the step (2) is performed only on the outermost partial batch shot area of the array area. Method. 6. The method according to claim 1, wherein the step (1) is performed between the step (1) and the step (2), before the earlier of the two steps, or between the two steps. 6. The electron beam drawing method according to claim 1, wherein a correction for the inter-graphic proximity effect is separately performed after any of the later processes. 7. The electron beam drawing method according to claim 6, wherein the correction for the inter-graphic proximity effect is performed by a ghost method.