JPH11329933A - Charged particle beam exposure system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deterioration of a block mask in a standby state, where no beams are applied to a sample to be exposed without stopping the beams, for a charged particle beam exposure system. SOLUTION: This system is provided with a block mask 2, where an opening for forming the section of a charged particle beam EB in a desired shape is formed, deflectors 3a and 3b for deflecting the beam EB on the block mask, and a means 4 for changing an application position on the block mask 2 of the beam EB by controlling the deflection of the deflectors. In a standby state, where no beam EB is applied onto the sample 1 to be exposed, a beam application position is appropriately changed on regions R1 -R4 where no opening is formed on the block mask 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus using a charged particle beam such as an electron beam, and more particularly to an exposure apparatus for drawing a pattern on a sample to be exposed (specifically, a wafer). The present invention relates to a technique useful for preventing deterioration of a block mask on which a transmission pattern (opening) is formed.

[0002]

2. Description of the Related Art In recent years, as the density of integrated circuits has increased, instead of photolithography, which has been the mainstream of forming fine patterns for many years, an exposure method using a charged particle beam such as an electron beam or an ion beam, or New exposure methods using lines have been considered and realized.

[0003] Among them, the electron beam exposure for forming a pattern by using an electron beam has a cross section of several tens of nanometers.
m, and a significant feature is that a fine pattern of 1 μm or less can be formed. However, since exposure using an electron beam is a so-called "one-stroke" drawing method, a finer pattern requires exposure with a smaller beam, which significantly increases the exposure time. Therefore, in order to solve such inconvenience, a block exposure method has been devised and put to practical use.

[0004] The block exposure method is to provide a block mask in which openings are formed in accordance with some basic patterns that are units of repetitive figures, and transmit a beam through desired openings in the block mask. In this method, a unit pattern is generated at a time, drawn on a sample to be exposed, and connected to repeatedly expose a figure. Therefore, such a block exposure method uses a 1 Gb (gigabit) DRAM.
This is an extremely effective method for exposing a pattern that is a repetition of a basic pattern that is small but has a large area to be exposed, such as a 4Gb DRAM.

In the conventionally known block exposure method, 1
Between the end of one exposure process and the start of the next exposure process, that is, in a standby state in which the beam is not irradiated onto the sample to be exposed, the irradiation position of the beam on the block mask is determined by the mask. It was fixed at the position where the beam is blocked, that is, the portion where the transmission pattern (opening) was not formed on the block mask.

[0006]

As described above, in the conventional block exposure method, when the sample to be exposed is in a standby state in which a beam is not irradiated (that is, when the exposure process is not performed), the block mask is used. Since the position where the beam is blocked is limited to one location on the block mask, the beam continues to be applied to the blocking position, resulting in local heating and deposition of impurities at that location, and consequently, The pattern on the block mask is deformed,
There is a problem that the block mask is deteriorated.

[0007] When the shape of the pattern on the block mask changes, the shape of the pattern finally drawn on the sample to be exposed also changes, which eventually leads to a decrease in exposure accuracy, which is not preferable. To address this,
For example, it is conceivable that the irradiation of the beam onto the block mask is stopped when the exposure processing is not performed. However, when the beam is stopped, it is necessary to perform operations such as initial setting of the beam deflection system again before starting the next exposure processing, which lowers the operation rate of the exposure apparatus and eventually lowers the throughput. Another problem arises.

The present invention has been made in view of such problems in the prior art, and is a charged particle beam capable of suppressing deterioration of a block mask in a standby state in which a beam is not irradiated onto a sample to be exposed without stopping the beam. An object of the present invention is to provide an exposure apparatus.

[0009]

FIGS. 1A and 1B show the principle of a charged particle beam exposure apparatus according to the present invention. FIG. 1A shows the configuration of the apparatus, and FIG. 1B shows the characteristic operation of the apparatus. Each is shown. In the drawing, EB denotes a charged particle beam (for example, an electron beam), 1 denotes a sample to be exposed (specifically, a wafer) on which a desired pattern is drawn by irradiation of the charged particle beam EB, and 2 denotes a cross section of the charged particle beam EB. A block mask in which an opening for forming into a desired shape is formed, 3
Reference numerals a, 3b, 3c, and 3d denote deflectors for deflecting the charged particle beam EB on the block mask 2. Strictly speaking, the deflector 3a arranged on the upstream side of the block mask 2
And 3b are charged particle beams EB on the block mask 2.
Is deflected, and the deflectors 3c and 3d arranged downstream of the block mask 2 have a function of returning the deflected charged particle beam EB to the original optical axis.

Reference numeral 4 denotes beam irradiation position changing means for controlling the deflection of each deflector (specifically, 3a and 3b) to change the irradiation position of the charged particle beam EB on the block mask 2, AP _{1 to} AP ₉ are regions where openings (transmission patterns) for forming the cross section of the charged particle beam EB into a desired shape are formed, and R _{1 to} R ₄ (hatched portions) are on the block mask 2 respectively. Indicates the position where the charged particle beam EB is cut off.

A feature of the present invention is that the charged particle beam EB is not stopped without stopping the charged particle beam EB in a standby state in which the charged particle beam EB is not irradiated on the sample 1 to be exposed, that is, when the exposure process is not performed. Thus, the position where the beam is irradiated (that is, the position where the beam EB is blocked by the mask 2) on the region where the opening (transmission pattern) is not formed is appropriately changed. FIG. 1 (b)
In the example, the beam irradiation position (that is, the beam cutoff position) is changed as R ₁ → R ₂ → R ₃ → R ₄ → R ₁ .

According to the present invention, the beam cutoff positions R _{1 to} R ₄ on the block mask 2 are appropriately changed in a standby state in which no beam is irradiated onto the sample 1 to be exposed. In 2, local heating and adhesion of impurities are appropriately dispersed, and a specific transmission pattern can be prevented from being deformed. This leads to suppression of the deterioration of the block mask 2 and thus greatly contributes to maintaining high-precision exposure.

Further, since there is no need to stop the charged particle beam EB, work such as initial setting of the beam deflection system is performed once once and thereafter becomes unnecessary, thereby lowering the operation rate of the exposure apparatus and, consequently, the throughput. Exposure processing can be performed without any need. When the beam irradiation position is changed from one beam cut-off position to another beam cut-off position on the block mask 2 in the standby state in which the beam is not irradiated onto the sample 1 to be exposed, the change path is changed to the opening forming region. It is desirable not to pass over. For example,
In the example of FIG. 1B, the beam irradiation position is changed from R ₁ to R _3.
, The change path passes over the three areas AP ₁ , AP ₅ and AP ₉ in which the openings are formed. In this case, there is a possibility that the beam is transmitted through the opening and finally irradiated onto the sample 1 to be exposed, and erroneous exposure is performed.

Therefore, in the charged particle beam exposure apparatus of the present invention, the beam irradiation position changing means 4 changes the beam irradiation position from one position to another position on the area where the opening is not formed on the block mask 2. When making the change, it is desirable to control the deflection of the deflectors 3a and 3b so that the change path does not pass over the formation region of the opening.

[0015]

FIG. 2 schematically shows a part of the structure of an electron beam exposure apparatus according to an embodiment of the present invention.
As shown, the electron beam exposure apparatus of the present embodiment includes an exposure unit 10 and a control unit 50.

The exposure section 10 has an electron gun 14 having a cathode electrode 11, a grid electrode 12, and an anode electrode 13 for emitting an electron beam, and a rectangular aperture (slit) for shaping the cross section of the electron beam into, for example, a rectangular shape. A mask 15, an electron lens 16 for converging the formed electron beam, a deflector 17 for deflecting a position at which the formed electron beam is irradiated onto the block mask 20 based on the corrected deflection signal HS, A pair of lenses 18 and 19 disposed opposite to each other along the flow direction of the laser beam, and an opening for movably disposed in a horizontal direction between the lenses and for shaping the cross section of the electron beam into a desired shape. A block mask 20 on which a (transmissive pattern) is formed, and arranged upstream and downstream with the block mask 20 interposed therebetween;
Deflectors 21 to 24 for deflecting the electron beam between the lenses 18 and 19 based on the mask irradiation position data PS1 to PS4 and selecting one of the transmission patterns formed on the block mask 20, respectively; Signal S
A blanking deflector 25 for blocking or transmitting the electron beam based on B, a lens 26 for reducing the cross section of the electron beam, and a mask 27 having a round aperture for shaping the cross section of the electron beam into a circular shape; A refocus coil 28 for correcting focusing, a projection lens 29 for irradiating the formed electron beam onto the wafer W, a dynamic focus coil 30 and a dynamic stig coil 31 for correcting the deflection of the electron beam. , Projection lens 32, and exposure position determination signal SS1
A main deflector 33 and a sub deflector 34 for positioning a beam on the wafer W based on
And a stage 35 which can be moved in the horizontal direction (X-Y direction), and alignment coils 36 to 39.

On the other hand, the control unit 50 includes a storage medium 51 storing design data of the integrated circuit device, a central processing unit (CPU) 52 for controlling the entire electron beam exposure apparatus, and a CPU
An interface 53 for transferring various information such as information on the drawing pattern captured by the device 52, information on a drawing position on the wafer W on which the pattern is to be drawn, and mask information of the block mask 20, and a drawing pattern transferred from the interface 53 A data memory 54 for storing information, mask information and the like, and an opening (transmission pattern) of the block mask 20 based on the information stored in the data memory, for example.
Is specified, and the block mask 20 of the specified pattern is specified.
In addition to generating mask irradiation position data P1 to P4 indicating the above position, generating wafer exposure position data S2 indicating a position on the wafer W where the pattern is exposed, the shape of the pattern to be drawn and the shape of the designated pattern Pattern generation unit 55 that performs processing for calculating a correction value H according to the difference
And generating a corrected deflection signal HS based on the correction value H from the pattern generation unit, converting the corrected deflection signal HS into an analog signal, and appropriately amplifying the signal.
AC & AMP (hereinafter simply referred to as “amplifier section”) 56
And mask irradiation position data P from the pattern generation unit 55
1 to P4 are converted to analog and mask irradiation position data PS
An amplifier unit 57 for generating and appropriately amplifying 1 to PS4, a mask moving mechanism 58 for moving the block mask 20 as necessary according to the output of the pattern generating unit 55, and an exposure time and an exposure waiting time from the pattern generating unit 55 A clock control circuit 59 for generating a system clock and a blanking clock on which the entire exposure apparatus operates based on the data of the present invention, and a blanking control for generating a blanking timing based on the blanking clock from the clock control circuit. Circuit 60 and a blanking signal S based on a blanking timing from the blanking control circuit.
An amplifier unit 6 that generates B, converts it to analog, and amplifies it appropriately
1, an amplifier unit 62 for controlling the refocus coil 28 based on the output of the pattern generation unit 55, and a data memory via the pattern generation block 55 based on the exposure start / end information transferred from the interface 53. In addition to outputting the deflection information for the main deflector to 54, a command is issued to the stage control unit 67 to move to the desired stage position, and the difference between the stage movement position and the main deflection amount is notified to the stage correction unit 70. The clock control circuit 59 is controlled to perform the
5, a sequence controller 63 for controlling a general sequence of the exposure processing such as control for generating / stopping a clock, and a deflection for generating a main deflector deflection signal S1 based on the main deflector deflection information from the data memory 54. A control circuit 64, and an amplifier unit 65 that generates exposure position determination signals SS1 and SS2 based on the output signal S1 from the deflection control circuit and the output signal S2 from the pattern generation unit 55, and performs analog conversion and appropriate amplification, and 66, a stage controller 67 for controlling the movement of the stage 35 based on the control from the sequence controller 63 (including a stage moving mechanism 68 for moving the stage 35, and a laser interferometer 69 for detecting the XY coordinate position of the stage 35). ), The main deflection amount output from the deflection control circuit 64 and the stage control unit 67 Amplifier 66 stage correction unit 70 supplies the difference to correct the the stage movement amount output
And

In the above configuration, the electron beam emitted from the electron gun 14 is shaped into a rectangular shape by slits formed in the mask 15, then converged by the lenses 16 and 18 and irradiated onto the block mask 20. You. The irradiated electron beam is appropriately deflected on the block mask 20.
More specifically, the deflection in a relatively large range (about 5 mm) on the block mask 20 means each of the deflectors 21 to 24 (beam deflection on the mask) disposed on both sides of the block mask 20. In this case, the deflection is performed by the deflectors 21 and 22, and the deflection in a relatively small range (about 500 μm) after the desired transmission pattern on the mask 20 is selected by the deflectors is performed by the deflector 17. Next, the electron beam transmitted through the desired transmission pattern on the block mask 20 is returned to the original optical axis by the deflectors 23 and 24, then converged by the lens 19, and further passes between the blanking deflector 25. After passing through, the cross section is reduced by the lens 26, and after passing through the round aperture of the mask 27, the projection lenses 29, 3
2 and is deflected by the sub deflector 34 in a small deflection area of about 100 μm. The sub deflection area is largely deflected by the main deflector 33 in an exposure field of about 2 mm.

On the other hand, the data to be subjected to the exposure processing is C
The data is read from the storage medium 51 by the PU 52 and stored in the data memory 54. When exposure is started by giving a start signal from the CPU 52 to the sequence controller 63, first, the data of the main deflector deflection position stored in the data memory 54 is sent to the deflection control circuit 64, and then the main deflector deflection signal S1 is output and supplied to the main deflector 33 via the amplifier section 65 as an exposure position determination signal SS1. Next, after the output value is stabilized, the sequence controller 63 controls the clock control circuit 59 to generate a system clock, whereby the pattern generation unit 55 causes the pattern data stored in the data memory 54 to be stored. Read. Pattern generator 55
Then, shot data is generated based on the read pattern data. Specifically, the shot data includes mask irradiation position data P1 to P4 indicating a beam irradiation position on the block mask 20;
A correction value H indicating the amount of deflection of the beam irradiation position on 0,
Wafer exposure position data S for deflecting the beam formed by transmitting the beam through the transmission pattern (opening) on the block mask 20 to a desired position on the wafer W
2. Shot time data, shot waiting time data indicating how long a waiting time is required for each deflector to settle when these signals are applied, and the like. After these signals are generated, they are input to a pattern correction unit (not shown) in the pattern generation unit 55 and are appropriately corrected. The pattern correction unit corrects wafer rotation or the like that occurs when the wafer W is set on the stage 35. The output signals for shot generation are input to the corresponding amplifier units 56, 57, 62, and 66, and are analog-converted and appropriately amplified, and then applied to each electrode or coil.

The operation described above is one mode of operation in performing a typical exposure process, and does not itself characterize the present embodiment. The feature of the electron beam exposure apparatus of the present embodiment is that, in addition to the above-described configuration and operation, when the wafer W is in a standby state in which the electron beam is not irradiated, that is, when the exposure process is not performed, the electron beam is stopped. Instead, the beam irradiation position (that is, the position where the electron beam is blocked by the mask 20) is appropriately changed on the region where the opening (transmission pattern) is not formed on the block mask 20.

For this reason, in the present embodiment, the CPU 52 that can recognize that the present exposure apparatus is in a standby state is provided.
(That is, since information for instructing start / end of exposure is transferred to the sequence controller 63 via the interface 53, the CPU 52 capable of recognizing whether the present exposure apparatus is currently performing the exposure processing) Is programmed in advance to control the deflectors 21 to 24 disposed on both sides of the block mask 20 to appropriately change the beam irradiation position (that is, the beam cutoff position) on the block mask 20. The contents of this programming, that is, the data that defines the processing procedure,
For example, it is stored in the storage medium 51, and when necessary, the CP
Enable U52 to capture the data.

As a specific operation, the mask information of the block mask 20 is fetched into the data memory 54 via the interface 53 by a command from the CPU 52 which recognizes that the exposure apparatus is in the standby state, and then the pattern generation is performed. The unit 55 specifies an area of the block mask 20 where the opening (transmission pattern) is not formed based on the mask information, generates mask irradiation position data P1 to P4 indicating the position of the specified area, and further generates an amplifier. Part 57
The mask irradiation position data P to each deflector 21 through 24
S <b> 1 to PS <b> 4 are supplied, and accordingly, the beam irradiation position is appropriately changed on a region where the transmission pattern is not formed on the block mask 20.

In programming, when the beam irradiation position is changed from one beam cut-off position to another beam cut-off position on the block mask 20, the changed path is prevented from passing over the transmission pattern forming area. It is desirable. This is to eliminate the possibility that the beam is transmitted through the transmission pattern in the standby state in which the beam is not irradiated on the wafer W and is finally irradiated on the wafer W to perform erroneous exposure as described above. .

In contrast to the principle configuration shown in FIG. 1, the sample 1 to be exposed corresponds to the wafer W, the block mask 2 corresponds to the block mask 20, and the deflectors 3a to 3d correspond to the deflectors 21 to 24. Corresponding, beam irradiation position changing means 4
Functionally corresponds to the CPU 52 and the pattern generator 55. As described above, according to the electron beam exposure apparatus of the present embodiment, the transmission pattern is not formed on the block mask 20 without stopping the beam in the standby state in which the beam is not irradiated onto the wafer W. Since the beam irradiation position is appropriately changed on the region, local heating and adhesion of impurities in the block mask 20 are appropriately dispersed, so that a specific transmission pattern can be prevented from being deformed. Thereby, the block mask 2
0 can be suppressed, which can contribute to maintaining high-precision exposure. Further, since there is no need to stop the beam, the operation such as the initial setting of the beam deflection system only needs to be performed once at the beginning, and as a result, the exposure process is performed without lowering the operation rate (that is, throughput) of the exposure apparatus. be able to.

FIG. 3 is a plan view showing the structure of the block mask 20, and FIG.
One area E _{k at} 0 (k = 1 to 9) is shown. As shown in FIG. 3, the block mask 20 has a large number of areas (9 areas E _{1 to} E _{9 in the} illustrated example) arranged in a matrix at a predetermined pitch EL.
The size of each area E ₁ to E _9, the size corresponding to the maximum deflection range of the beam irradiated onto the block mask 20,
For example, the length of one side of the area is selected to be about 1 mm to 5 mm. Also, the reference points of each area E _{1 to} E ₉ (in the figure, ●
) Are given XY coordinate values, respectively.
For example, when the area coordinates E _XY = (1, 1), it is assumed that the area E ₇ is represented.

On the other hand, as shown in FIG.
_{In k} , a large number of blocks (36 blocks B ₁ to B _{1 in the} illustrated example) are arranged in a matrix at a predetermined pitch interval BL.
B ₃₆ ) are arranged. The size of each of the blocks B _{1 to} B ₃₆ is selected to be a size corresponding to the cross-sectional area of the beam irradiated on the block mask 20, for example, the length of one side of the block is about 100 μm to 500 μm. The reference point of each block B1～B ₃₆ and XY coordinate values are given respectively to the (point indicated in FIG ●), for example, when the block coordinates B _XY = (2,1), the block B ₃₂ It shall be expressed.

As described above, by designating the area coordinates E _XY and the block coordinates B _XY , an arbitrary block in an arbitrary area can be expressed. For example, E _XY = (1,1),
If B _XY = (2,1), the block B ₃₂ in the area E ₇ is designated. 3 and 4, hatched blocks (B) located at four corners of each area are shown.
₁ , B ₆ , B ₃₁ , and B ₃₆ ) indicate openings for a variable rectangle.

FIG. 5 shows an example of a transmission pattern formed in each block in each area. In the figure, B _i , B _j ,
_Bm and _Bn indicate blocks, respectively, and are indicated by hatchings 20a, 20b, 20c, 20d, 20e, and 20.
f and 20g each represent a transmission pattern (opening). FIG. 6 illustrates the relationship between the wafer and its moving direction in the continuous stage moving method.

The IC pattern or the like exposed on the wafer W usually has a size of about 5 mm to 20 mm, and it is necessary to expose a fine pattern with high precision. It is practically impossible to expose two IC patterns without moving the stage. Therefore, I
Exposure needs to be performed by dividing the C pattern into a plurality of exposure fields. In this case, the stage movement is frequently repeated, and the throughput of the entire exposure apparatus is reduced. The continuous stage moving method has been devised to cope with such inconvenience.

In the continuous stage moving method, as shown in FIG. 6, an IC pattern is formed on a wafer W and a range in which exposure can be performed by one continuous stage movement (ST portion indicated by hatching in the figure). As one exposure range (hereinafter, referred to as “stripe”). Here, the width of the stripe ST corresponds to a beam deflection range that can be deflected by the main deflector 33 that performs beam positioning on the wafer W based on the exposure position determination signal S1 (see FIG. 2). The movement of the stage 35 on which the wafer W is mounted is performed by the stage controller 67 as described above. The stage 35 is provided with a DC motor (not shown) for driving the stage in each of the X-axis and Y-axis directions orthogonal to each other, and a laser interferometer 69. The direction, moving speed, yawing amount, etc. are constantly measured. In FIG. 6, C shown by hatching
The HP portion indicates a region corresponding to one chip.

In the above embodiment, the exposure apparatus using an electron beam has been described. However, as is clear from the gist of the present invention, a charged particle beam is sufficient as a beam to be used. Of course, it is possible.

[0032]

As described above, according to the charged particle beam exposure apparatus of the present invention, in the standby state in which the beam is not irradiated onto the sample to be exposed, the beam is not stopped and the aperture is opened on the block mask. By appropriately changing the beam irradiation position (that is, the beam blocking position) on the region where the portion (transmission pattern) is not formed, local heating on the mask and adhesion of impurities can be appropriately dispersed.
This can prevent a specific transmission pattern from being deformed and suppress the deterioration of the block mask. This greatly contributes to maintaining high-precision exposure.

Further, since there is no need to stop the beam, the operation such as initial setting of the beam deflecting system only needs to be performed once at first, and as a result, the exposure processing can be performed without lowering the throughput of the exposure apparatus. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of a charged particle beam exposure apparatus according to the present invention.

FIG. 2 is a block diagram schematically showing a part of the configuration of an electron beam exposure apparatus according to one embodiment of the present invention.

FIG. 3 is a plan view showing a configuration of a block mask in FIG. 2;

FIG. 4 is a diagram showing one area in the block mask of FIG. 3;

FIG. 5 is a diagram showing an example of a transmission pattern formed in each block in the area of FIG. 4;

FIG. 6 is a diagram for explaining a relationship between a wafer and its moving direction in a continuous stage moving method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exposed sample (wafer) 2 ... Block mask 3a, 3b ... (deflects a beam on a block mask) Deflector 3c, 3d ... (returns the deflected beam to the original optical axis)
Deflector 4 ... beam irradiation position changing means AP ₁ ~AP ₉ ... opening region (transmission pattern) is formed EB ... charged particle beam (e.g., electron beam) R ₁ to R ₄ ... beam blocking position

Claims (2)

[Claims] 1. A block mask having an opening for forming a cross section of a charged particle beam into a desired shape, a deflector for deflecting the charged particle beam on the block mask, and a deflection of the deflector Beam irradiation position changing means for controlling the irradiation position of the charged particle beam on the block mask by controlling the charged particle beam. The beam irradiation position changing means does not irradiate the charged particle beam on the sample to be exposed. A charged particle beam exposure apparatus, wherein in a standby state, deflection of the deflector is controlled so as to appropriately change a beam irradiation position on a region where the opening is not formed on the block mask. 2. The charged particle beam exposure apparatus according to claim 1, wherein the beam irradiation position changing unit changes the beam irradiation position from one position on an area where the opening is not formed on the block mask. A charged particle beam exposure apparatus, wherein when changing the position to another position, the deflection of the deflector is controlled so that the change path does not pass over the formation region of the opening.