JPH0837146A - Method and apparatus for electron beam exposure - Google Patents

Abstract

PURPOSE:To correct the approximate effect with the data processing within a short period of time by correcting unbalance in amount of exposure by electron beam generated during the main exposure by the approximate effect between patterns through auxiliary exposure with a constant dose for each region including a plurality of patterns. CONSTITUTION:Exposing data is converted, by a pattern generator 8, to pattern exposing data for main exposure with an electron beam aligner. During this period, the data of width W and height H in the primary memory 12 for area are multiplied by a multiplier 9 and then accumulated with an accumulator 12 and are then inputted to an arithmetic unit 13. Meanwhile, the number of patterns N in a subfield is called from the primary memory 7 and is then inputted to the arithmetic unit 13. In the arithmetic unit 13, dose of auxiliary exposure is computed. After the main exposure is completed, the subfield is immediately exposed as the auxiliary exposure with the dose computed above in order to complete the exposure for the entire part of the main field.

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 an electron beam exposure apparatus which are characterized by a method for correcting the proximity effect. When forming a pattern of an integrated circuit device or the like on a semiconductor wafer, an exposure mask or reticle having the pattern is manufactured, and the exposure mask or reticle is moved by an aligner or stepper, and the pattern is transferred to the semiconductor wafer. The technique of exposing on top of the photoresist coating above is widely used.

In the process of manufacturing this exposure mask or reticle, a light-shielding film such as Cr is formed on a transparent substrate, and when this light-shielding film is selectively removed, an electron beam sensitive resist is formed on the light-shielding film. An electron beam exposure method in which a film is formed and a fine electron beam is irradiated on the film is widely used. In this specification, irradiation of an electron beam onto an electron beam sensitive resist film formed on a light-shielding film on a substrate is performed in accordance with a custom in this technical field in accordance with a light exposure technique. It will be referred to as "electron beam exposure", "exposure", and the like.

Further, in the case of high-mix low-volume production and short-term delivery, the electron beam sensitive resist coating formed on a semiconductor wafer is also directly irradiated with an electron beam to expose a pattern.

[0004]

2. Description of the Related Art In a process of manufacturing a mask or a reticle for exposing a pattern by electron beam exposure, forward scattering (scattering in the traveling direction of the electron beam) and back scattering (traveling of the electron beam) in a transparent substrate of the reticle. It is known that a phenomenon called "proximity effect" of the electron beam occurs due to scattering in the direction opposite to the direction.

That is, when a pattern is exposed to an electron beam, in a region where the pattern density is high, scattered electrons transmitted through an adjacent pattern are irradiated with an electron beam at a level sufficient to expose the electron beam sensitive resist film to the outside of the pattern. As a result, the pattern becomes slightly larger, and in the area where the isolated pattern exists, it is only affected by the scattered electrons that have passed through the pattern, and the level is sufficient to expose the electron beam sensitive resist film to the outside of the pattern. Since the electron beam is not generated, the phenomenon that the pattern becomes large does not occur.

Therefore, the finished size of the pattern such as a mask or a resist varies depending on the pattern shape, the density, etc., but the effect of causing an error in the finished size of the pattern due to scattered electrons is This is called the "proximity effect" of the electron beam.

Generally, in the electron beam exposure apparatus,
Electron beam sensitive resist by electrostatic deflection capable of high-speed operation of a beam spot with a diameter of about 0.1 μm, a variable rectangular beam with a maximum of about 2 μm square, and a block electron beam that passes through a preformed aperture of the same size. After irradiating on the film and exposing the pattern in the 100 μm × 100 μm subfield, the electron beam is electromagnetically deflected to the central part of the other subfield in the blanked state, and the electron beam is tranquilized as described above. An exposure method is adopted in which the exposure of the pattern in the main frame is completed by repeating the exposure of the pattern in the subfield by electric deflection.

The size of the main frame is about 20 mm square in the case of direct writing, and about 100 mm square, which is five times that in the case of a mask or reticle.

Conventionally, a method called an exposure amount correction method is known as one of the methods for correcting the proximity effect. For each pattern, the proximity effect is calculated one by one from the size and shape of the pattern, the size and shape and spacing of the pattern in the vicinity of the pattern, the energy of the electron beam, the sensitivity of the resist, etc. This is a method in which the optimum exposure amount is determined based on this, and the exposure amount is specified for each pattern data in the pattern file of the electron beam exposure apparatus.

FIG. 3 is an explanatory view of a proximity effect correction method by a conventional electron beam exposure apparatus. 31 in this figure is CP
U and 32 are magnetic tape devices, 33 is a magnetic disk device,
Reference numeral 34 is a console, 35 is an interface, 36 is a primary storage device, 37 is a pattern generator, 38 is a proximity effect correction processing device, and 39 is a large-scale general-purpose computer.

In the proximity effect correction method by the conventional electron beam exposure apparatus schematically shown in this figure, the CPU 31 receives data stored in the magnetic tape device 32 according to an instruction input from the console 34. From the inside
The exposure data of the pattern to be exposed and the proximity effect correction data are called and stored in the magnetic disk device 33 that can operate at higher speed.

Further, according to an instruction input from the console 34, the exposure data and the proximity effect correction data are stored in the primary storage device 36 which is a semiconductor storage device which can be randomly accessed at high speed from the interface 35.
This exposure data includes a figure code, XY position information, pattern width W, height H, and the like.

This exposure data is converted into pattern exposure data by the pattern generator 37, and the exposure amount for correcting the proximity effect is determined for each pattern by the proximity effect correction processing device 38. The electron beam sensitive resist coating is exposed according to the corrected exposure dose.

In this case, the exposure data conversion processing for converting the design data into the exposure data, and the proximity effect correction processing device 3
The proximity effect correction data for correction in 8 is separately processed by the large-scale general-purpose computer 39.

According to this method, the exposure data conversion process from the design data to the exposure data is performed, and then the proximity effect correction process is performed for each pattern to expose each pattern with the optimum exposure amount. Therefore, in theory, the proximity effect is used. Can be effectively corrected.

[0016]

However, according to this conventional proximity effect correction processing, for example, when an electron beam is incident on a resist-formed wafer at an acceleration voltage of 20 kV, the proximity of the electron beam within a radius of 4 μm is reached. If there is an influence of the effect, a range with a radius of 4 μm is divided into 0.1 μm grids centering on a certain pattern, and rearward generated from other 0.1 μm × 0.1 μm unit patterns existing in the range. Since it is necessary to calculate the influence of electrons due to scattering and forward scattering, and then perform similar calculations for other patterns, there is a problem that the calculation takes a long time.

The calculation of this proximity effect correction data is performed by the CPU.
Even if the data is monopolized, it takes about 7 times as long as the normal exposure data conversion process, and if time sharing is used, even if a high-speed computer is used, it takes time on a daily basis, and the pattern density is The higher the temperature, the more time it takes.

An object of the present invention is to provide a means capable of correcting the proximity effect caused by electron beam exposure in the manufacturing process of a semiconductor device by data processing in a relatively short time.

[0019]

In the electron beam exposure method according to the present invention, the imbalance of the exposure amount of the electron beam generated during the main exposure due to the proximity effect between the patterns is corrected for each region including a plurality of patterns. A step of correcting by adopting auxiliary exposure with a fixed dose amount was adopted.

In this case, the total exposure area can be calculated for each region including a plurality of patterns at the time of main exposure, and the auxiliary exposure can be performed with a dose amount according to the calculation result.

Further, in this case, the total exposure area and the number of patterns can be calculated for each region including a plurality of patterns during the main exposure, and the auxiliary exposure can be performed with a dose amount according to the calculation result.

Further, in the electron beam exposure apparatus according to the present invention, a means for calculating the total exposure area for each area including a plurality of patterns at the time of main exposure and a dose amount for the auxiliary exposure are calculated according to the calculation result. Means and means for auxiliary exposure of a region including a plurality of patterns with a constant dose amount in accordance with the calculation result are adopted.

In another electron beam exposure apparatus according to the present invention, means for calculating the total exposure area and the number of patterns for each area including a plurality of patterns at the time of main exposure,
A structure having means for calculating the dose amount of auxiliary exposure according to the calculation result and means for performing auxiliary exposure for the region including the plurality of patterns with a constant dose amount according to the calculation result is adopted.

Further, in these cases, a region including a plurality of patterns can be set as a subfield within a range that can be deflected by electrostatic deflection.

[0025]

In the electron beam exposure apparatus of the present invention, the imbalance of the exposure amount of the electron beam caused during the main exposure due to the proximity effect of the electron beam can be deflected by a region including a plurality of patterns, for example, electrostatic deflection. For each subfield, the total exposure area of a plurality of patterns included in the area, or the total exposure area and the number of patterns are calculated, and correction is performed by performing auxiliary exposure with a constant dose amount according to the calculation result. Is characterized by.

According to the electron beam exposure apparatus using the proximity effect correction method, the exposure time is long because the main exposure and the auxiliary exposure are performed, but only an exposure data conversion process is performed by an external general-purpose computer, which requires a long time. Since the sum of the areas of the patterns within the predetermined range is calculated or the number of patterns is simply counted in the electron beam exposure apparatus without performing the proximity effect correction process, the throughput can be significantly improved.

Here, the principle of determining the dose amount of the auxiliary exposure for compensating the proximity effect in the electron beam exposure apparatus of the present invention will be described. In the pattern file of the electron beam exposure apparatus, the shape of the pattern to be subjected to electron beam exposure, for example, the shape of a rectangle, parallelogram, or triangle is stored as a pattern code, and the width W and height H of each pattern are stored. are doing. Therefore, the area can be calculated from the pattern code and the width W and height H of each pattern. For example, the area of each pattern can be calculated as W × H for a rectangle, W × H for a parallelogram, and W × H × 1/2 for a triangle.

In this way, it is possible to integrate (ΣS) the areas of the patterns in a region including a plurality of patterns which are, for example, subfields. Also, in the process of this calculation,
The number of patterns existing in the area can be counted.

The dose amount D _c of the auxiliary exposure is the dose amount D _o of the main exposure and the total area (ΣS) obtained by calculation or experiment on the typified pattern, or the total area (ΣS) and the pattern It can be determined using the relationship between the number (N) and the proper auxiliary exposure. That is,
Dose amount D _c = f (ΣS, N) × D _o D _o : main exposure amount

With this dose amount D _c , an area including a plurality of patterns, which is, for example, a subfield, is subjected to auxiliary exposure, and when the auxiliary exposure in the area is completed, main exposure and auxiliary exposure of the next area are sequentially performed. , The whole (main field) is exposed.

According to the experimental example, the time required to process all data, which conventionally took a long time, is reduced to 1/5 to 1/7, and the electron beam exposure time is increased by about 10 to 20%. It has been found that the throughput of the is improved by about 30 to 40%.

[0032]

Embodiments of the present invention will be described below. (First Embodiment) FIG. 1 is an explanatory view of a proximity effect correction method by an electron beam exposure apparatus of the first embodiment. In this figure, 1 is a CPU, 2 is a magnetic tape device, 3 is a magnetic disk device,
4 is a console, 5 is an interface, 6 is an area primary storage device, 7 is a number primary storage device, 8 is a pattern generator, 9 is a multiplier, 10 is a selector, 11 is a variable multiplier, 12 is an integrator, Reference numeral 13 is an arithmetic unit, and 14 is a large-scale general-purpose computer.

In the proximity effect correction method by the electron beam exposure apparatus of the first embodiment shown in this figure, the CPU 1 is instructed by the instruction input from the console 4 to change the data stored in the magnetic tape apparatus 2. The exposure data of the pattern to be exposed is retrieved from the inside and stored in the magnetic disk device 3 which can operate at higher speed.

Next, the exposure data is stored in the area primary storage device 6 and the number primary storage device 7 which are semiconductor storage devices which can be randomly accessed at high speed through the interface 5. The exposure data includes a figure code, XY position information, pattern width W, height H, number N, and the like.

This exposure data is converted by the pattern generator 8 into pattern exposure data for main exposure by the electron beam exposure apparatus, and a fixed dose amount (D _o 100
%) To mainly expose the pattern in the subfield.

The data of the width W and the height H of the pattern in the area primary storage device 6 are multiplied by the multiplier 9 within the time during which the pattern in this subfield is mainly exposed.
If the pattern is rectangular or parallelogram,
When the variable multiplier 11 is set to “× 1” by the selector 10 responding to the figure code and the pattern is a triangle,
The area of the pattern is calculated by setting the variable multiplier 11 to “× ½”. Then, the areas of the patterns calculated in this way are integrated by the integrator 12, and the result is input to the calculator 13.

FIG. 2 is an explanatory diagram of the exposure pattern in the subfield. 21 in this figure is a subfield frame, 2
2 is a rectangular exposure pattern, 23 is a triangular exposure pattern, and 24 is a parallelogram exposure pattern.

A process of calculating the area of the exposure pattern by the above-mentioned multiplier 9, selector 10 and variable multiplier 11 will be described. It is assumed that the subfield frame 21 has a rectangular exposure pattern 22, a triangular exposure pattern 23, and a parallelogram exposure pattern 24.

First, with respect to the rectangular exposure pattern 22, the width W = a and the height H = b are multiplied by the multiplier 9, and the variable multiplier is changed by the selector 10 which responds to the graphic code indicating that it is rectangular. The value is set to “× 1” and input to the integrator 12 as it is.

For the triangular exposure pattern 23, the width W = c and the height H = d are multiplied by the multiplier 9, and the variable multiplier is changed by the selector 10 responding to the figure code indicating the triangle. "X1 / 2", c
And the product of d is halved and input to the integrator 12.

As for the parallelogram exposure pattern 24, as in the case of the rectangle, the width W = e and the height H = f are multiplied by the multiplier 9 to indicate that it is a parallelogram. The variable multiplier is set to “× 1” by the selector 10 that responds to the code, and is input to the integrator 12 as it is. In this integrator 12, the total area of the exposure pattern is integrated as ΣS = a × b + c × d / 2 + e × f.

On the other hand, the number N of patterns in the subfield is called from the number primary storage device 7 and input to the arithmetic unit 13.

In the calculator 13, for example, the dose amount (D _c ) of the auxiliary exposure is calculated according to the following formula. D _c = (αN + β / ΣS) × D _o This α and β can be determined by calculating using a typified pattern and correcting by experiment.

In this case, the reason why "αN" is added is that the large number N of patterns means that small patterns such as contact holes are often isolated and exist in the main exposure. Since it is considered that the influence of scattered electrons is small, it is necessary to increase the dose amount of auxiliary exposure by that amount. However, this α may become negative depending on the pattern mode.

Since this calculation can be performed within the time during which the main exposure is being performed, immediately after the main exposure is completed, the subfield is supplementally exposed with this dose amount. When the auxiliary exposure in this subfield is completed, the main exposure of the next subfield is performed, then the auxiliary exposure is performed, and this is repeated to complete the exposure of the entire main field.

This auxiliary exposure is carried out in the same exposure apparatus as the main exposure with a fixed dose amount determined by calculation, and a maximum of 2 μm.
Solid coating is performed so that the required dose can be obtained with an m-square or 4 μm-square electron beam, but the auxiliary exposure does not require very high dimensional accuracy, so the maximum size of the electron-beam optical system is a 20 μm-square electron beam. Can also be filled with

It is difficult to expect a compensation effect equivalent to the proximity effect compensation method of the above-mentioned conventional electron beam exposure apparatus by the electron beam exposure apparatus of this embodiment, but the data processing by the large general-purpose computer is Only the conversion process, the proximity effect correction process that takes a long time uses the data processed by the conventional electron beam exposure apparatus,
Since it is replaced with the calculation process of the dose amount of the auxiliary exposure which can be processed in a short time, the total exposure process time can be significantly shortened.

In this embodiment, the dose amount of auxiliary exposure is calculated by D _c = (αN + β / ΣS) × D _o . However, depending on the pattern, αN may be omitted and D _c may be omitted.
Even if = (β / ΣS) × D _o , the effect of auxiliary exposure can be obtained, and the term of N × ΣS can be added.

(Second Embodiment) In the electron beam exposure method of the first embodiment, the dose amount of the auxiliary exposure for compensating the proximity effect has been described as being calculated by an empirical formula.
In the electron beam exposure method of this embodiment, instead of this, an accumulated area of the exposure pattern, or an accumulated area of the exposure pattern, the number of exposure patterns, and a target table of the proper dose amount of auxiliary exposure are accumulated, and this table is stored in this table. By accessing, the proper dose amount of auxiliary exposure is determined.

The proximity effect compensating method for the electron beam exposure apparatus of the present invention, like a memory device such as a RAM or a ROM, has a mode such as an area or a space of a pattern in a region including a plurality of subfield patterns. It is particularly effective in the case where the memory cell area and the logic circuit area are substantially uniform, but when there are extremely different patterns in the area, a dummy pattern having a form substantially similar to the exposure pattern is formed. By doing so, the dose amount of the auxiliary exposure for compensating the proximity effect can be optimized.

Further, in each of the above-mentioned embodiments, the auxiliary exposure is performed for each subfield constituting the main field. However, depending on the form of the apparatus for which the exposure accuracy is desired to be improved, the pattern accuracy is within a permissible range. It is possible to collectively perform auxiliary exposure with the same dose amount on regions including a plurality of patterns having the maximum area to be accommodated in. In an extreme case, the memory cell area and the logic circuit area of the memory device may be supplementarily exposed with the same dose amount.

[0052]

As described above, according to the electron beam exposure apparatus of the present invention, the proximity effect of the electron beam can be compensated by a small number of steps or time in the process of manufacturing the exposure reticle or wafer. In the field of manufacturing technology for high-density integrated circuit devices, it will make a great contribution.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a proximity effect correction method by an electron beam exposure apparatus according to a first embodiment.

FIG. 2 is an explanatory diagram of an exposure pattern in a subfield.

FIG. 3 is an explanatory diagram of a proximity effect correction method using a conventional electron beam exposure apparatus.

[Explanation of symbols]

 1 CPU 2 magnetic tape device 3 magnetic disk device 4 console 5 interface 6 area primary storage device 7 number primary storage device 8 pattern generator 9 multiplier 10 selector 11 variable multiplier 12 integrator 13 calculator 14 large-scale general-purpose computer 21 Subfield frame 22 Rectangular exposure pattern 23 Triangle exposure pattern 24 Parallelogram exposure pattern

Claims (7)

[Claims] 1. An imbalance in the exposure amount of an electron beam generated during main exposure due to a proximity effect between patterns is corrected by supplementary exposure with a constant dose amount for each region including a plurality of patterns. And electron beam exposure method. 2. The electronic device according to claim 1, wherein the total exposure area is calculated for each region including a plurality of patterns at the time of main exposure, and the auxiliary exposure is performed with a dose amount according to the calculation result. Beam exposure method. 3. The total exposure area and the number of patterns are calculated for each area including a plurality of patterns during the main exposure, and the auxiliary exposure is performed with a dose amount according to the calculation result. Electron beam exposure method. 4. The electron beam according to claim 1, wherein the region including the plurality of patterns is a subfield within a range that can be deflected by electrostatic deflection. Exposure method. 5. A means for calculating a total exposure area for each area including a plurality of patterns at the time of main exposure, a means for calculating a dose amount of auxiliary exposure according to the calculation result, and a means for calculating the dose amount of auxiliary exposure according to the calculation result. An electron beam exposure apparatus comprising means for auxiliary exposure of a region including a plurality of patterns with a constant dose amount. 6. A means for calculating the total exposure area and the number of patterns for each area including a plurality of patterns at the time of main exposure, a means for calculating the dose amount of auxiliary exposure according to the calculation result, and the calculation result. An electron beam exposure apparatus having means for auxiliary exposure of a region including the plurality of patterns at a fixed dose according to the above. 7. The electron beam exposure apparatus according to claim 5, wherein the region including the plurality of patterns is a subfield within a range that can be deflected by electrostatic deflection.