JP2000195781A - Making of block mask for electronic beam exposure device and block mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce failure rates by decreasing the effect of deviation in a method of making a block mask by exposing an aperture pattern using an electronic beam exposure device. SOLUTION: There is provided a method of making a block mask for an electronic beam exposure device wherein the block mask which has a plurality of areas and patterns with holes formed on each area is exposed using the electronic beam exposure device with a plurality of deflecting means such as a main deflector, sub-deflector, and sub-subdeflector. This method comprises steps 101, 105 and 109 of determining the minimum deflection range which is minimum among the deflection ranges larger than the area in the deflection range of each deflecting means, steps 103 and 107 of dividing the area into a plurality of exposed areas smaller than the minimum deflection range, wherein each area is divided to enter in a single exposed area, and steps 104 and 108 of exposing the pattern with holes within each exposed area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a block mask for an electron beam exposure apparatus, and more particularly to a method for forming a block mask using an electron beam exposure apparatus.

[0002]

2. Description of the Related Art Semiconductor integrated circuits tend to be more highly integrated with advances in microfabrication technology, and the performance required of microfabrication technology is becoming increasingly severe. In particular, in the case of the exposure technology, the limit of the light exposure technology used for the steppers and the like conventionally used is expected. Electron beam exposure technology is a technology that is likely to be the next generation of fine processing in place of light exposure technology.

There are various types of electron beam exposure apparatuses such as a variable rectangular exposure system, a block exposure system, and a multi-beam exposure system. The block exposure method is a method in which a pattern serving as a unit of a repeated figure is held on a transmission mask, an electron beam is transmitted through the mask to generate a unit pattern at a time, and the pattern is connected to expose the figure repeatedly. FIG. 1 is a diagram showing the configuration of a beam irradiation system in a block exposure type electron beam exposure apparatus. In FIG. 1, reference numeral 1
1 is an electron gun for generating an electron beam, 12 is an electron gun 11
A first converging lens that converts the electron beam from the laser beam into a parallel beam, an aperture 13 that shapes the passing parallel beam into a predetermined shape, 14 a second converging lens that narrows the formed beam, and 15 a forming lens 16 is a first mask deflector, 17 is a deflector for dynamically correcting astigmatism caused by a mask, 18 is a second mask deflector, 19 is
Denotes a converging coil for a mask, 20 denotes a first shaping lens, 21 denotes a block mask moved by a mask stage 21A, 22 denotes a second shaping lens, and 23 denotes a third shaping lens.
, A blanking deflector for turning on / off the beam, 25 a fourth max deflector, 26 a third lens, 27 a circular aperture, and 28 a reduction A lens, 29 a dynamic focus coil, 30 a projection lens, 31 an electromagnetic main deflector, 32 an electrostatic sub deflector, 33 a same electrostatic deflector 32 as the sub deflector 32 The deflector is a sub / sub deflector having a faster response speed than the sub deflector 32 but a narrower deflection range. The electron beam 10 is converged on the sample (wafer) 1 placed on the stage 2 by the projection lens 30. Stage is wafer 1
Is moved two-dimensionally in a plane perpendicular to the electron beam 10. The above parts are accommodated in a housing called an electron optical column (column), and the inside of the column is evacuated to perform exposure. The electron beam exposure apparatus further has an exposure control unit that controls each part of the column so as to expose a desired pattern. Since the above configuration is widely known, the description is omitted here.

FIG. 2 is a diagram for explaining the block mask 21 described above. The block mask 21 is, for example, a silicon substrate 21 such as a wafer, and a plurality of blocks 51 (16 in the figure) are further processed by etching or the like so as to have a thickness of about 20 μm. Each block 51 is further provided with a plurality of areas 52, each of which is provided with a hole corresponding to a unit pattern which is a unit of a repeated figure, and this hole is referred to as a hole. The range of the electron beam that can be deflected to select the aperture is limited, and a plurality of blocks 51 are provided corresponding to this range. In each block 51, a large number of areas 52 each having an aperture pattern are provided. Is provided. Any area within each block 51 can be arbitrarily selected in a very short time. If it is necessary to use the opening in another block 51, the mask stage 2
1A, the block mask 21 is moved and the block 51 is moved.
Is located in the optical path of the electron beam.

[0005] The opening pattern is a simple pattern such as an area 52a having a small opening as shown in the figure, an area 52b having a large opening, a rectangular (rectangular) opening, or an opening combining rectangles. In addition to the area with
In some cases, an area having a complicated pattern extracted from the IC repetition pattern is provided. Further, there may be a case where an all-open area through which an electron beam for a variable rectangular portion described later passes is provided.

[0006] The block mask 21 is made using a silicon substrate. The block 51 of the silicon substrate is processed to a thickness of about 20 μm, and an oxide film is provided thereon. A resist layer is applied on the silicon substrate, and a pattern corresponding to the opening is exposed. Thereafter, development is performed, and the exposed portion of the resist is removed, so that a hole corresponding to the opening is formed in the resist layer. In this state, plasma etching is performed from the side where the resist is applied. As a result, the oxide film at the hole portion is removed, and only the hole portion is etched, so that a hole corresponding to the exposure pattern, that is, an opening is formed on the silicon substrate. Block mask 2
Since the electron beam that has passed through the first aperture is reduced and irradiated, the aperture of the block mask 21 may be larger than the pattern at the time of exposure, and the aperture pattern can be exposed even by photolithography, but is more precise. To expose the pattern, it is desirable to use an electron beam exposure apparatus.

The present invention relates to a method of manufacturing a block mask for exposing an opening pattern of a block mask for an electron beam exposure apparatus by an electron beam exposure apparatus. The electron beam exposure apparatus to be used may be a block exposure system or a conventional single beam scanning and exposing system. In the electron beam exposure apparatus of FIG. 1, a main deflector 31, a sub deflector 32, and a sub / sub deflector 33 are provided as deflection means for changing the irradiation position (deflection position) of the electron beam on the sample. I have. Also, as a means for mounting the sample (silicon substrate) 1 and moving it with respect to the electron beam irradiation system,
Is provided. It suffices if one deflecting means can deflect a wide range at high speed and with high accuracy. However, in general, a wide deflection range tends to decrease the response speed and the deflection position accuracy. For example, the main deflector 31 is an electromagnetic deflector, the sub deflector 32 and the sub / sub deflector 33 are electrostatic deflectors, and the main deflector 31 is a sub deflector 32 and a sub / sub deflector. Although the deflection range is larger than that of the device 33, the response speed is slow. The sub / sub deflector 33 is an electrostatic deflector similar to the sub deflector 32. However, since the deflection range is narrower than the sub deflector 32, the amplitude of the drive signal is small, and the corresponding drive signal is generated. The response speed of the sub-deflector 32 is faster than the response speed of the drive signal generator of the sub deflector 32. Therefore, the sub / sub deflector 33 has a narrower deflection range than the sub deflector 32 but has a higher response speed. As described above, the change range (deflection range) of the irradiation position of the deflecting unit is determined by the main deflector 31, the sub deflector 32,
The response speed decreases in the order of the sub / sub deflectors 33, and the response speed increases in the order of the main deflector 31, the sub deflector 32, and the sub / sub deflector 33.

In an electron beam exposure apparatus, in order to perform exposure efficiently, exposure is performed by combining a plurality of deflection means having different characteristics as described above. For example, assuming that three stages of deflection means are combined, the deflection range of the first deflection means is the widest field, the deflection range of the second deflection means is a sub-field, and the deflection range of the third deflection means is Subfield. As shown in FIG. 3, the field 61 is divided into subfields 62, and the subfield 62 is further divided into sub / subfields 63. When exposing inside a certain subfield 62, FIG.
As shown in (1), the deflection position of the first deflecting means is fixed at the center position of the subfield 62, and
After the deflection position of the deflecting means is fixed at the center position A of the sub-sub-field 63, the exposure in the sub-sub-field 63 is performed by changing the deflecting position B of the third deflecting means. When the exposure in a certain sub-subfield 63 is completed, the deflection position of the second deflecting means is fixed to the center position of the adjacent sub-subfield 63, and the deflection of the third deflecting means is similarly performed. The exposure in the sub-sub-field 63 is performed by changing the position. At this time, the first
The deflection position of the deflection means is fixed. By performing such an operation for all the sub-sub-fields 63 in the sub-field 62, the exposure of the sub-field 62 is completed. Next, the same operation is performed after changing the deflection position of the first deflecting means to be the center position of the adjacent subfield 62, and such an operation is performed for all the subfields 62 in the field 61. For example, the exposure of the field 61 ends. According to such an exposure method, it is not necessary to frequently change the deflection position of the deflection means having a low response speed, so that the exposure time can be shortened.

In the electron beam exposure apparatus shown in FIG. 1, the deflection range of the main deflector 31 corresponds to a field, the deflection range of the sub deflector 32 corresponds to a subfield, and
The deflection range of the sub deflector 33 corresponds to a sub subfield. In the electron beam exposure apparatus shown in FIG. 1, the main deflector 31, the sub-deflector 32, and the sub-sub-deflector 33 are provided as three-stage deflectors. In some cases, only the deflector 32 is provided. In that case, there will be no sub-subfield.

[0010]

Generally, when the irradiation position is changed by the deflecting means, the positional accuracy (accuracy of the deflecting position) is determined in the order of the main deflector 31, the sub deflector 32, and the sub / sub deflector 33. And become smaller. Since the deflection position error is related to the deflection amount, the deflection position error tends to increase as the deflection amount increases, even if the deflection position accuracy of the deflection means is the same.

FIG. 5 is a view for explaining division of an exposure region when an opening pattern of the block mask 21 used in the electron beam exposure apparatus as shown in FIG. 2 is exposed by the electron beam exposure apparatus. Multiple areas 52 in a block
Is shown. In the exposure of the block mask 21, the exposure time is required to be as short as possible in order to improve the production efficiency. Therefore, as described with reference to FIG. 3, exposure is performed by dividing the block into a plurality of exposure regions. For example, a block has 4 rows arranged in 7 rows and 7 columns.
If there are nine areas 52 and the block size is larger than the sub-field corresponding to the deflection range of the sub deflector and smaller than the sub-field corresponding to the deflection range of the main deflector, as shown in FIG. It is most efficient to divide the block into a plurality of (4 × 4 in this case) sub-subfields 63 for exposure. With such a division, some areas 52 will be exposed in different sub-sub-fields 63.

In FIG. 5, the portion indicated by reference numeral 53 is:
There is a pattern as shown in FIG. 6, and a portion 71a is exposed at the time of exposure in one sub-sub-field 63a,
It is assumed that a portion 71b is exposed at the time of exposure in another sub-subfield 63b. If there is no deflection position error between the two sub-subfields 63a and 63b, exposure is performed as shown in (1). However, in the two sub-subfields 63a and 63b, the deflection position of the main deflector is fixed at the center of each sub-subfield 63a and 63b, and the exposure is performed by changing the deflection position of the sub-deflector. In the exposure of the two sub-subfields 63a and 63b, there is a large difference in the deflection position of the main deflector. As described above, since the error is related to the magnitude of the deflection amount, it is inevitable that a certain error occurs in the deflection position of the main deflector when exposing the two sub-subfields 63a and 63b. . Also, regarding the sub deflector, the amount of deflection when exposing the patterns 71a and 71b is opposite to the amount of positive / negative deflection. Of course, if the error is sufficiently small, a pattern substantially as shown in FIG. 6A can be obtained, but if the error becomes too large to be ignored, the pattern as shown in FIGS. become.

FIG. 6B shows patterns 71a and 71b.
Is a case where the two sub-subfields are shifted in the horizontal direction, (3) is a case where the two sub-subfields are shifted in the vertical direction, and (4) is a case where the two sub-subfields are shifted in the vertical direction. It is a case where it shifted. (5) is a pattern obtained in the case of (4), and the line width of the overlapping portion becomes thick. Actually, a shift such as (2) to (4) occurs in combination.

The block mask is an opening pattern which is the basis of an exposure pattern. If there is an error in this opening pattern, all the patterns exposed by an electron beam exposure apparatus using this block mask will have errors. For example, if there is a shift as shown in (2) to (4) in FIG. 6 in the hole pattern of the block mask, it may cause disconnection or the like. Therefore, the aperture pattern of the block mask is required to be a very accurate pattern. If the block mask has a defect even at one location, the block mask itself becomes a defective product. Therefore, if a shift as shown in (2) to (4) of FIG. Problem.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and a more accurate opening method is provided in a manufacturing method of exposing an opening pattern of a block mask for an electron beam exposure apparatus using an electron beam exposure apparatus. It is intended to obtain a hole pattern.

[0016]

In order to achieve the above object, in the method of forming a block mask for an electron beam exposure apparatus according to the present invention, when exposing a block mask to a plurality of exposure regions and exposing the same, an aperture pattern is formed. Each of the areas is not divided by a plurality of exposure areas corresponding to a deflection range larger than this area, and each area is exposed by a single exposure area.

That is, the method of producing a block mask for an electron beam exposure apparatus according to the present invention comprises a plurality of deflecting means for changing the irradiation position of an electron beam on a sample, and each deflecting means has a different deflection range. An electron beam exposure apparatus having a plurality of areas, and an aperture pattern formed in each area, using an electron beam exposure apparatus that combines the deflection amounts of the deflection means to achieve a desired deflection amount as a whole. A method for producing a block mask for an electron beam exposure apparatus that exposes an opening pattern of a block mask, comprising: a step of determining a minimum minimum deflection range within a deflection range larger than an area in a deflection range of each deflection unit; A step of dividing a plurality of areas of the block mask for the electron beam exposure apparatus into a plurality of exposure areas smaller than the minimum deflection range,
A step of dividing each area so as to fall within a single exposure area, and fixing the opening amount pattern in each exposure area to a constant amount of deflection by a deflection means having a minimum deflection range and a larger variation range. Exposing at the top.

According to the present invention, since each area is only divided into the minimum required exposure range, an error in a connection portion of the exposure range is reduced, and an accurate aperture pattern with a small error can be obtained. The shift shown in FIG. 6 is a problem at the connection portion of the exposure area. If the shift is within the same exposure area, the shift gradually shifts, so that the deterioration of the aperture pattern due to the shift hardly causes a problem.

For example, when the moving range by the main deflector is the first range, the deflection range by the sub deflector is the second range, and the deflection range by the sub and sub deflectors is the third range, and each area is smaller than the third range. In the sub area, do not cross each area
A subfield is determined, a subfield is determined in a range smaller than the second range by combining a plurality of sub-subfields, and a field is determined in a range smaller than the first range by combining a plurality of subfields. One or more areas may be included in each sub-subfield. However, considering efficiency, it is desirable that the number of areas included in each sub-subfield is as large as possible.

When each area is smaller than the second range,
Determine the subfield so that it does not cross each area,
A field is determined in a range smaller than the first range by combining a plurality of subfields. In this case, since the area is exposed in a plurality of sub-sub-fields,
In the adjacent part of the subfield, a shift occurs due to an error in the position of the two sub-subfields.
Deterioration is small compared to the case where there is a shift due to an error in the position of two sub-fields or a shift due to an error in the position of the two sub-fields only due to an error in the position of one sub-sub-field. When the area is divided into a plurality of sub-subfields, it is desirable to determine the boundaries of the sub-subfields so that the boundaries of the sub-subfields do not cross the pattern, particularly a thin pattern. For example, when there are a plurality of independent aperture patterns in one area, the boundaries are determined so that the independent aperture patterns are included in one sub-subfield as much as possible. The exposure area is not limited to a square or a rectangle, and may have any shape as long as it is within the deflection range of one unit.

Of course, by dividing into the above-described exposure areas, the number of exposure areas may be increased as compared with the conventional case where the exposure areas are determined mechanically,
In such a case, the time required for exposure increases. However, a block mask has a smaller requirement for throughput and a greater requirement for accuracy than a case where a normal semiconductor device is exposed, and therefore, there is a great advantage in applying the present invention.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. The electron beam exposure apparatus used in this embodiment has a configuration as shown in FIG. 1, and the prepared block mask is also used in FIG. Is what is done. The block mask is shown in FIG.
Are similar to those shown in FIG.
And each block 51 has an area 52 as shown in FIG.
Having. In FIG. 7, an area indicated by reference numeral 53 is an opening for a variable rectangle, which is provided with a large opening. The electron beam passing therethrough is directed to a variable rectangular portion which can be adjusted to a shape obtained by combining various rectangles. Can be In each area 52, an opening pattern corresponding to a basic pattern used repeatedly from an exposure pattern of an IC to be used for exposure is formed, and a desired exposure pattern can be obtained by combining them.

FIGS. 8 and 9 are flowcharts showing the exposure processing in the embodiment. In the following description, the deflection range by the main deflector is referred to as a first range, the deflection range by the sub deflector is referred to as a second range, and the deflection range by the sub and sub deflectors is referred to as a third range. In step 101, it is determined whether or not the area 52 of the block mask of FIG. 7 is smaller than the third range.
Go to 05. In step 102, the vertical
The maximum number of horizontal areas (m, n) is determined.
Divides the block vertically and horizontally into sub-subfields having an area of (m, n). In step 104, the moving position of the stage, the deflecting position of the main deflector, and the deflecting position of the sub-deflector are fixed so that the combined irradiation position is at the center of each sub-sub-field. The aperture pattern of the area in the sub-subfield is exposed while changing the deflection position of the detector. This completes the exposure processing.

In step 105, it is determined whether the area is smaller than the second range. If the area is smaller, the process proceeds to step 106, and if larger, the process proceeds to step 109. Step 106
Then, the maximum number of vertical and horizontal areas that fall within the second range (o, p)
Is determined, and in step 107, the blocks are arranged vertically and horizontally (o,
The subfield is divided into subfields having the area of p). In step 108, the moving position of the stage and the deflection position of the main deflector are fixed so that the irradiation position is at the center of each subfield by combining them. The aperture pattern of the area in the sub-field is exposed while changing the deflection position of the deflector and the sub / sub-deflectors. This completes the exposure processing.

In step 109, it is determined whether the area is smaller than the first range. If the area is smaller, the process proceeds to step 110, and if larger, the process proceeds to step 113. Step 110
Then, the maximum number of vertical and horizontal areas that fall within the first range (q, r)
Is determined, and in step 111, the blocks are arranged vertically and horizontally (q,
r) split into fields with areas of
In step 12, while the moving position of the stage is fixed at the center of each field, the aperture pattern of the area in the subfield is exposed while changing the deflection positions of the main deflector, the sub deflector, and the sub / sub deflectors. This completes the exposure processing.

In step 113, the opening pattern of each area is exposed while changing the moving position of the stage and the deflecting positions of the main deflector and the sub deflector. 10 and 11
FIG. 4 is a diagram showing an example of an exposure area divided as described above. FIG. 10A shows a case in which the area 52 is smaller than the deflection range of the sub-sub-deflector, and the exposure range is determined so that one area 52 is included in each sub-sub-field 63. (2) is a case where the area 52 is similarly smaller than the deflection range of the sub / sub deflector. However, the exposure range is determined so that four areas 52 are included in each sub / sub field 63.

FIG. 11 shows a case where the area 52 is larger than the deflection range of the sub-sub-deflector but smaller than the deflection range of the sub-deflector, and the exposure range is set so that one area 52 is included in each sub-field 62. Has been determined. Since each subfield 62 is divided into nine sub-subfields 63, each area 52 is exposed by nine sub-subfields 63.

In the case shown in FIG. 11, each area 52 is exposed in nine sub-sub-fields 63.
At the connection portion of the subfield 63, there is a possibility that a shift as shown in FIG. 6 may occur. Even in such a case, since each area is not exposed to a plurality of subfields 62, the occurrence of defects is reduced as compared with the related art.
The position of the sub-subfield 63 is affected by the error. However, even in such a case, depending on the aperture pattern, the sub-sub-field 63 can be determined so as not to be affected or reduced by the error of the position of the sub-sub-field 63. Hereinafter, such an example will be described.

FIG. 12 shows a case where there are a plurality of independent aperture patterns 80a to 80d in one area, and the deflection range by the sub deflector is the range 81 shown in (2).
In this case, the area is set to a sub-
It is conceivable to divide the data into subfields 82a to 82d. However, in this division, since there is a boundary in the middle of the pattern, a problem of a shift as shown in FIG. 6 occurs.
Therefore, the sub-sub-fields 83a to 83d are shown in FIG.
(4). of course,
The sub-subfields 83a to 83d fall within the range 81. In this case, four independent opening patterns 80a
To 80d are sub / subfields 83a to 83d, respectively.
Since it falls within 3d, the problem of displacement does not occur.

FIG. 13 shows an example in which the aperture pattern 84 is divided into four sub-subfields 85a to 85d and exposed. In this case as well, the sub-sub-fields 83a to 83a
3d falls within the deflection range 81 by the sub deflector. The problem of the displacement as shown in FIG. 6 significantly affects the case of a thin pattern. If the division is performed as shown in FIG. 12, all the thin patterns fall within the sub-sub-field 83d, so that the influence of the displacement can be reduced.

What has been described with reference to FIGS. 10 to 13 is the same when the area 52 is larger than the deflection range of the sub deflector but smaller than the deflection range of the main deflector.

[0032]

As described above, according to the present invention,
When the aperture pattern of the block mask for the electron beam exposure apparatus is exposed using the electron beam exposure apparatus, the influence of the displacement of the connection portion of the exposure area can be reduced, so that a more accurate aperture pattern can be obtained. The defective rate in the production of a block mask can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an electron optical column of an electron beam exposure apparatus.

FIG. 2 is a diagram showing a block mask.

FIG. 3 is a view for explaining a method of efficiently performing exposure by combining means for deflecting an electron beam with a different deflection range onto a sample.

FIG. 4 is a view for explaining how to change the deflection position in the method of FIG. 3;

5 is a diagram showing a conventional example of dividing an exposure area when exposing a block mask by the method of FIG. 3;

FIG. 6 is a diagram illustrating a problem when exposure is performed by the method of FIG. 3;

FIG. 7 is a diagram showing an example of an arrangement of areas of a block mask manufactured in the embodiment.

FIG. 8 is a flowchart illustrating an exposure process in the embodiment.

FIG. 9 is a flowchart illustrating an exposure process in the embodiment.

FIG. 10 is a diagram showing an example in which an exposure region is divided by applying the present invention.

FIG. 11 is a diagram showing an example in which an exposure region is divided by applying the present invention.

FIG. 12 is a diagram showing a modification of division of an exposure area.

FIG. 13 is a diagram showing a modification of division of an exposure area.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sample (wafer) 11 ... Electron gun 16, 18, 23, 25 ... Mask deflector 21 ... Block mask 28 ... Reduction lens 29 ... Dynamic focus lens 30 ... Projection lens 31 ... Main deflector 31a-31d ... Electromagnetic deflector 32 ... sub-deflector 33 ... sub-sub-deflector 51 ... block 52 ... area 61 ... field 62 ... sub-field 63 ... sub-sub-field

Claims (2)

[Claims] A plurality of deflecting means for changing an irradiation position of an electron beam on a sample, wherein the deflecting ranges of the deflecting means are different from each other; An electron beam exposure apparatus for exposing the aperture pattern of an electron beam exposure apparatus block mask having a plurality of areas and an aperture pattern formed in each area using an electron beam exposure apparatus for realizing a deflection amount Determining a minimum minimum deflection range within a deflection range larger than the area in a deflection range of each deflection unit, and a method of forming the plurality of block masks for the electron beam exposure apparatus. Dividing the area into a plurality of exposure areas smaller than the minimum deflection range, wherein each area is divided into a single exposure area. Exposing the aperture pattern in each exposure area after fixing the amount of deflection by the deflection means having the minimum deflection range and a larger deflection range to a fixed value. A method for producing a block mask for a beam exposure apparatus. 2. A block mask for an electron beam exposure apparatus produced by the method for producing a block mask for an electron beam exposure apparatus according to claim 1.