Patent Application
20140131589
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-247696, filed on Nov. 9, 2012, the entire contents of which are incorporated herein by reference.
The present invention relates to an electron beam exposure apparatus and an electron beam exposure method.
Methods for exposing a pattern with electron beams include variable shaped beam (VSB) methods and character projection (CP) methods.
These exposure methods cut an electron beam emitted from an electron gun with a beam shaping section including a rectangular opening and further cut off a part of the cut electron beam with another beam shaping section to provide electron beams shaped into various profiles. The shaped electron beam is then reduced by 20- to 50-fold with an electron lens system and is then projected onto an exposure object.
In order to increase the throughput of exposure in such a process of electron beam exposure, it is effective to increase the range capable of being irradiated with one beam shot to reduce the number of times of beam irradiation and to increase the current density of the electron beam to shorten the exposure time.
However, increasing the area irradiated with an electron beam and the current density thereof can increase the influence of the coulomb interaction between electrons in the electron beam, thus causing a blur of the electron beam. Accordingly, edge roughness of the resist pattern formed by the exposure is increased.
Patent Document 1: Japanese Laid-open Patent Publication No. 2004-88071
Patent Document 2: Japanese Laid-open Patent Publication No. 2001-274077
Patent Document 2: Japanese Laid-open Patent Publication No. 2007-184398
Non-Patent Document 1: “Evaluation of throughput improvement and character projection in multi-column-cell E-beam exposure system”, Akio Yamada et al., Proc of SPIE, Vol. 7748 774816-4
Accordingly, it is an object in one aspect of the invention to provide an electron beam exposure apparatus to minimize the blur of the electron beam even if the current density of the electron beam is increased.
An aspect of the present invention provides an electron beam exposure apparatus, including: an electron gun configured to emit an electron beam; a first beam shaping portion having a first opening configured to shape the electron beam; a first deflector configured to deflect the electron beam having passed through the first opening; a second beam shaping portion having a second opening configured to allow a part of the electron beam having passed through the first opening to pass through; a second deflector configured to deflect the electron beam having passed through the second opening; a third beam shaping portion having a third opening configured to allow a part of the electron beam having passed through the second opening to pass through; and a controller configured to control the first and second deflectors to prevent an edge of the electron beam formed by the first opening from being included in the electron beam having passed through the third opening, and to allow the electron beam to be shaped by only the second and third openings.
According to the electron beam exposure apparatus of the above aspect, in the process of shaping a fine beam, the current value of the electron beam having passed through the second opening is smaller than that of the original electron beam having passed through the first opening. Accordingly, when the edge of the electron beam formed by the first opening is removed by the second and third beam shaping portions, it is possible to suppress the blur of the electron beam due to the coulomb interaction and to therefore draw fine patterns with high accuracy.
A description is given of the underlying prelude prior to the description of embodiments.
The beam shaping section of the VSB-type electron beam exposure apparatus shown in
As illustrated by a shaded area in
Next, as illustrated in
In this process, a part of the image of the first aperture 103a by the electron beam EB1 which overlaps a second aperture 140a is clipped as illustrated by a shaded area in
The thus-shaped electron beam EB2 is reduced by 20- to 50-fold with a not-shown electron optical system and is then projected onto the surface of a sample as an exposure object.
As described above, the electron beam EB2 formed by the beam shaping section of the electron beam exposure apparatus of
To be specific, edges a1 and a2 of the electron beam EB2 illustrated in
Each edge herein refers to an edge of an image of the corresponding aperture appearing at a cross-section of the focused electron beam.
In order to increase the throughput of the electron beam exposure apparatus, it is required to increase the area irradiated with an electron beam at one shot and to increase the current density of the electron beam. Accordingly, it is necessary to increase the current of the electron beam.
For example, consideration is given to an electron beam which is projected with a size of 1 μm×1 μm at maximum and a current density of 100 A/cm2 at the surface of a sample as the exposure object.
In this case, the electron beam EB1 which passes through the first aperture 103a needs to have the following current based on the current conservation low
1 μm×1 μm×100 A/cm2−1 μA (1)
With such a comparatively large current, the interaction due to coulomb force between electrons included in the electron beam has large influence, thus causing large blur at the edges a1 and a2 of the electron beam EB1 cut by the first aperture 103a.
As shown in
The blur appearing at the second beam shaping portion 140 is reduced by 20- to 50-fold with an electron optical system to be projected onto the surface of the sample, but the size of blur is still 13 to 32 nm on the sample as the exposure object. The blur derived from the electron beam EB1 cut by the first aperture 103a appears as edge roughness of drawn patterns.
In the case of forming fine patterns with line widths of 11 to 18 nm with the electron beam exposure, for example, it is preferable that the blur at the edge of the electron beam projected onto the sample as the exposure object is less than 10 nm.
Accordingly, it is difficult for an electron beam exposure apparatus including the electron beam shaping section of
The same problem occurs also in CP-type electron beam exposure apparatus.
In the beam shaping section of the CP-type electron beam exposure apparatus illustrated in
The electron beam EB1, which is formed by the first beam shaping portion 103, is positioned by CP mask deflectors 124a and 124b and is then focused onto a predetermined opening pattern of a CP exposure mask 110 by electromagnetic lenses 105 and 108.
As illustrated in
In some types of CP exposure process, the size of the electron beam EB2 is changed by projecting the electron beam EB1 so that the electron beam EB1 overlaps a part of the opening pattern 110c as illustrated in
In such a case, edges a1 and a2 of the electron beam EB2 are edges cut by the first beam shaping portion 103 and therefore significantly blur.
In the drawing, the edge a5 at the right side of the line pattern is thicker than the edge a4 at the left side of the line pattern. This shows that the edge roughness of the edge a5 in the width direction is greater than that of the edge a4.
Hereinbelow, embodiments are described.
As illustrated in
As illustrated in
As illustrated in
Between the first and second beam shaping portions 103 and 140, first and second electromagnetic lenses 105 and 107 are provided. The first and second electromagnetic lenses 105 and 107 are configured to focus the electron beam EB1 onto the second beam shaping portion 140 are provided. Moreover, between the first and second electromagnetic lenses 105 and 107, a first deflector 104 and a first alignment portion 508 are provided. The first deflector 104 and first alignment portion 508 are configured to adjust the focusing position of the electron beam EB1 are provided.
As illustrated in
Furthermore, as illustrated in
The electron beam EB2 is deflected to a predetermined position on the third beam shaping portion 150 by the second deflector 111 and second alignment portion 509 and is focused onto the third beam shaping portion 150 by the third electromagnetic lens 112.
As illustrated in
In the above-described manner, an electron beam EB3 having a rectangular cross section illustrated in
As illustrated in
The sample chamber 71 is provided with a sample stage 72 movable in the horizontal direction with a motor or the like. The sample 73 as an exposure object is fixed on the sample stage 72. By moving the sample stage 72, the entire surface of the sample 73 can be exposed.
The control section 31 includes an electron gun controller 202, an electron optical system controller 203, a deflection controller 204, a blanking controller 206, and a stage controller 207. The electron gun controller 202 controls the electron gun 101 for control of the acceleration voltage and current density of the electron beam EB0 and the like.
The electron optical system controller 203 controls the electromagnetic lenses 105, 107, and 112 and the objective lens 120.
The blanking controller 206 controls the voltage to a blanking electrode (not shown) which determines whether to project the electron beam EB3 to prevent the electron beam EB3 from being projected onto the sample 73 before exposure.
The stage controller 207 moves the sample stage 72 so that the electron beam EB3 is projected onto a desired position of the sample 73.
The deflection controller 204 reads exposure data from the exposure data memory 23 and creates beam size data and exposure position data. The beam size data and exposure position data respectively indicate the size of the electron beam and the irradiation position of the electron beam on the sample for each shot.
The deflection controller 204 includes: a first deflection correcting portion 211 and a second deflection correcting portion 212 which operate based on the beam size data; and an exposure position controller 213 which operates based on the exposure position data. The first deflection correcting portion 211 outputs control signals to the first deflector 104 and first alignment portion 508 through a driver 211a. The second deflection correcting portion 212 outputs control signals to the second deflector 111 and second alignment portion 509 through a driver 212a.
The exposure position controller 213 sets a predetermined deflection output to an exposure position deflector 119 through a driver 213a based on the exposure position data.
The exposure data giving an operation instruction to each controller of the control section 31 is created by the integrated control system 21. The integrated control system 21 is a computer, such as a work station, for example. The integrated control system 21 is configured to create exposure data of each shot based on design data indicating a pattern to be exposed. The integrated control system 21 transfers the created exposure data to the exposure data memory 23 through a bus 22.
Hereinbelow, a description is given of operation of the first and second deflection correcting portions 211 and 212.
The first and second deflection correcting portions 211 and 212 respectively set referential outputs to the first and second alignment portions 508 and 509 which correspond to the beam size data of referential beam size (S0x, S0y). The referential beam size (S0x, S0y) is a size of a rectangle having a certain magnitude. When the referential outputs are inputted to the first and second alignment portions 508 and 509, an electron beam having the referential beam size (S0x, S0y) is formed.
For example, as indicated by a dashed line of
Moreover, as indicated by a dashed line of
The beam size (Sx, Sy) is therefore set to (0, 0) before the outputs to the first and second deflectors 104 and 111 are set.
The referential beam size (S0x, S0y) is unnecessarily 0 and may be set equal to the size of the second and third apertures 140a and 150a, for example. In this case, the first deflection correcting portion 211 sets the output for the first alignment portion 508 so that the lower left corner of the image by the electron beam EB1 on the second beam shaping portion 140 matches the lower left corner of the second aperture 140a. Moreover, the second deflection correcting portion 212 sets the output for the second alignment portion 509 so that the upper right corner of the image by the electron beam EB2 on the third beam shaping portion 150 matches the upper right corner of the third aperture 150a.
Next, a description is given of a case of increasing the beam size to (Sx, Sy) when the referential beam size (S0x, S0y) is 0.
In this case, the first deflection correcting portion 211 sets the predetermined output for the first deflector 104 to deflect the electron beam EB1 so that the image by the electron beam EB1 on the second beam shaping portion 140 moves to the lower left with respect to the second aperture 140a. This allows a part of the electron beam EB2 having a predetermined size to pass through the second beam shaping portion 140 as indicated by the shaded portion of
Moreover, the second deflection correcting portion 212 sets a predetermined output for the second deflector 111 to deflect the electron beam EB2 so that the image by the electron beam EB2 on the third beam shaping portion 150 moves to the upper right with respect to the third aperture 150a. This forms the electron beam EB3 having the beam size (Sx, Sy) as indicated by the shaded portion of
On the other hand, when the size of the referential beam size (S0x, S0y) is equal to the second and third apertures 140a and 150a, the beam size is reduced to (Sx, Sy) in the following manner.
In this case, the first deflection correcting portion 211 sets the output for the first deflector 104 so that the lower left corner of the image by the electron beam EB1 on the second beam shaping portion 140 moves to the upper right by a predetermined distance. Moreover, the second deflection correcting portion 212 sets the output for the second deflector 111 so that the upper right corner of the image by the electron beam EB2 on the third beam shaping portion 150 moves to the lower left by a predetermined distance.
In the case of changing the beam size in this embodiment, as described above, the first and second defectors 104 and 111 are configured to deflect an electron beam in the directions opposite to each other. Accordingly, the electron beam EB3 can be always prevented from including the edge cut by the first beam shaping portion 103.
As illustrated in
The current value of the electron beam EB2 passing through the second aperture 140a and the current value of the electron beam EB3 passing through the third aperture 150a are smaller than the current value of the electron beam EB1. Accordingly, the coulomb interaction has small influence between the second and third beam shaping portions 140 and 150 and between the third beam shaping portion 150 and the sample 73 as the exposure object.
According to the electron beam exposure apparatus 100 of the first embodiment, it is possible to reduce blur due to the coulomb effect at the edges 53a, 53b, 53c, and 53d of the electron beam EB3. The surface of the sample 73 can be irradiated with a sharp electron beam having a large current density.
According to the electron beam exposure apparatus 100 of the above-described embodiment, it is possible to increase the exposure throughput while minimizing blur of the electron beam.
Hereinbelow, a description is given of an electron beam exposure method using the electron beam exposure apparatus 100.
As illustrated in
Next, the exposure process proceeds to step S11 of
Next, the process proceeds to step S12. Based on the exposure data, the deflection controller 204 of the control section 31 (see
The process then proceeds to step S13. The first and second deflection correcting portions 211 and 212 of the control section 31 set outputs necessary to output an electron beam of the size specified by the beam size data.
The outputs to the first and second alignment portions 508 and 509 are set by the method previously described with reference to
The first and second deflection correcting portions 211 and 212 set the outputs for the first and second deflectors 104 and 111 by carrying out the following calculation processing corresponding to coordinate conversion for the inputted beam size data (Sx, Sy).
The first deflection correcting portion 211 calculates a correction value S1x in the direction x and a correction value S1y in the direction y for the first deflector 104 based on the following equations.
S
1x
=G
1x·(Sx−S0x)+R1x·(Sy−S0y)+H1x·(Sx−S0x)·(Sy−S0y)+O1x (1)
S
1y
=G
1y·(Sy−S0y)+R1y·(Sx−S0x)+H1y·(Sy−S0y)·(Sx−S0x)+O1y (2)
The second deflection correcting portion 212 calculates a correction value S2x in the direction x and a correction value S2y in the direction y for the second deflector 111 based on the following equations.
S
2x
=G
2x·(Sx−S0x)+R2x·(Sy−S0y)+H2x·(Sx−S0x)·(Sy−S0y)+O2x (3)
S
2y
=G
2y·(Sy−S0y)+R2y·(Sx−S0x)+H2y·(Sy−S0y)·(Sx−S0x)+O2y (4)
Herein, G is a correction coefficient for the magnification; R, a correction coefficient for the rotational component; H, a correction coefficient for the distortion component; and O, a correction coefficient for the offset component.
(S0x, S0y) is the referential beam size. When the beam size data (Sx, Sy) is equal to the referential beam size (S0x, S0y), the outputs to the first and second deflectors 104 and 111 after the correction calculation are substantially zero. At this time, the outputs for the first and second alignment portions 508 and 509 are set so that the electron beam EB3 on the sample 73 as the exposure object has a size obtained by reducing the referential beam size (S0x, S0y) by a predetermined magnification and so that the electron beams are projected onto different corners of the second and third apertures 140a and 150a.
Furthermore, the coefficients G1x, R1x, H1x, G1y, R1y, and H1y and the coefficients G2x, R2x, H2x, G2y, R2y, and H2y are properly set, so that the edge of the electron beam EB3 on the sample 73 is always formed of only edges cut by the second and third apertures 140a and 150a.
Moreover, in step S13, the exposure position correcting portion 213 calculates a deflection output for the exposure position deflector 119 based on the exposure position data (X, Y) by the following equations. Herein, Xout and Yout represent deflection outputs in the directions X and Y for the exposure position deflector 119.
X
out
=g
x
·X+r
x
·Y+h
x
·X·Y+o
x (5)
Y
out
=g
y
·Y+r
y
·X+h
y
·X·Y+o
y (6)
Next, the process proceeds to step S14. The drivers 211a, 212a, and 213a of the control section 31 respectively give the deflection outputs corresponding to the correction values calculated by the correcting portions 211, 212, and 213 to the first alignment portion 508 and first deflector 104, the second alignment portion 509 and second deflector 111, and the exposure position deflector 119.
The size and irradiation position of the electron beam EB3 are thus determined to complete preparation for exposure.
Thereafter, the process proceeds to step S15. The blanking controller 206 of the control section 31 activates a blanker (not shown) only for a predetermined time to project the electron beam EB3 onto the sample 73.
One beam shot is thus completed.
The process then proceeds to step S16. The control section 31 reads next exposure data from the exposure data memory and determines whether exposure to be performed at the current stage position is finished. In step S16, if the control section 31 determines that the exposure at the current stage position is not finished (NO), the process proceeds to step S12, and the exposure is performed based on the next exposure data.
If the control section 31 determines in step S16 that the exposure at the current stage position is finished (YES), the process proceeds to step S17.
In the next step S17, the control section 31 determines based on the exposure data whether exposure of the entire sample is completed. If the control section 31 determines that exposure for the entire sample is not completed (NO), the process proceeds to the step S11, and the stage controller 207 of the control section 31 moves the sample stage 72 so that the sample 73 is moved to the next stage position.
On the other hand, if the control section 31 determines in the step S17 that exposure for the entire sample is completed (YES), the exposure process is terminated.
In such a manner, electron beam exposure according to the first embodiment is completed.
According to the first embodiment, the edge of the electron beam EB3 projected onto the sample 73 does not include the edge cut by the first aperture 103a having large blur. Accordingly, the blur of an electron beam can be minimized even if the current density of the electron beam is increased. It is therefore possible to shorten the time of irradiation of the electron beam in the step S15 while maintaining the high accuracy, thus increasing the throughput.
An electron beam exposure apparatus 200 according to the second embodiment differs from the VSB-type electron beam exposure apparatus 100 illustrated in
As illustrated in
The beam shaping section 81a includes a CP mask 110 having a plurality of opening patterns. CP mask deflectors 124a and 124b are used to select one of the opening patterns in the CP mask 110, and an electron beam EB3 passes through the selected opening pattern and is then returned to the optical axis by return deflectors 125a and 125b.
An electromagnetic lens 118, an exposure position deflector 119, an objective lens 120, and a sample chamber 71 are the same as those of the electron beam exposure apparatus 100 of
On the other hand, a control section 32 differs from the control section 31 of
On the other hand, the deflection controller 204 reads exposure data from an exposure data memory 23 and creates beam size data that specify the beam size of each shot, exposure position data that specify the irradiation position of the electron beam, and CP selection deflection data that specify the opening pattern.
A beam size deflection data correcting portion 221 performs correction calculation for the beam size data, which corresponds to the coordinate conversion to the irradiation position of the electron beam on the second beam shaping portion 140. A beam size deflection data correcting portion 222 performs correction calculation for the beam size data, which corresponds to the coordinate conversion to the irradiation position of the electron beam on the CP exposure mask 110. Moreover, a CP selection deflection data correcting portion 223 performs correction calculation corresponding to the coordinate conversion to the irradiation position on the CP exposure mask 110 based on the CP selection deflection data and sets outputs for the CP mask deflectors 124a and 124b. Furthermore, a CP selection deflection data correcting portion 224 calculates output values to the return deflectors 125a and 125b.
An exposure position data correcting portion 225 performs correction calculation corresponding to the coordinate conversion for the exposure position data.
The calculation results of the aforementioned correcting portions 221, 222, 223, 224, and 225 are outputted through drivers 221a, 223a, 224a, and 225a as driving powers of the deflectors 104, 125, and 119. The calculation results of the beam size deflection data correcting portion 222 and the CP selection deflection data correcting portion 223 are previously added up and inputted to the driver 223a.
Hereinbelow, a description is given of a method of shaping an electron beam by the electron beam exposure apparatus 200.
As illustrated in
Next, the electron beam EB1 is guided onto a second aperture 140a of the second beam shaping portion 140 by the first deflector 104 and a first alignment portion 508. The image of a first aperture 103a is formed on the second beam shaping portion 140 by the electromagnetic lenses 105 and 107. A part of the electron beam EB1 is cut by the second aperture 140a to be shaped into an electron beam EB2 having a rectangular cross-section as illustrated in
As illustrated in
In this embodiment, the size of the electron beam is changed around previously set referential beam size (S0x, S0y) . To change the beam size (Sx, Sy), the irradiation position of the electron beam EB1 on the second beam shaping portion 140, which is moved by the first deflector 104, and the irradiation position of the electron beam EB2 on the CP exposure mask 110, which is moved by the CP mask deflectors 124a and 124b, are moved in the directions opposite to each other.
As illustrated in
According to the second embodiment, it is possible to prevent the influence of blur of the electron beam EB1 and perform highly-accurate exposure with the high current density maintained.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-247696 | Nov 2012 | JP | national |
