Beam grid layout

Abstract

A sub-beam aperture array for forming a plurality of sub-beams from one or more charged particle beams. The sub-beam aperture array comprises one or more beam areas, each beam area comprising a plurality of sub-beam apertures arranged in a non-regular hexagonal pattern, the sub-beam apertures arranged so that, when projected in a first direction onto a line parallel to a second direction, the sub-beam apertures are uniformly spaced along the line, and wherein the first direction is different from the second direction. The system further comprises a beamlet aperture array with a plurality of beamlet apertures arranged in one or more groups. The beamlet aperture array is arranged to receive the sub-beams and form a plurality of beamlets at the locations of the beamlet apertures of the beamlet array.

Description

CROSS REFERENCE TO RELATED APPLICATION

This
app_yoffset=(−pitch/2)+[(6−[(num−1)mod 7]+int(num/29)−3)*pitch]−[(pitch/7)*(int[(num−1)/7)]−3)];
where app_xoffset and app_yoffset express the X and Y-axis offset from center point 710, num=aperture number, and int[ ] is a floor function that maps a real number to the largest previous integer, including 0.

FIGS. 10A and 10B illustrate only one embodiment. Alternative arrangements of unbalanced arrays, number of apertures, row and column pitches, and intra-row offset values are within the scope of the invention.

FIG. 11A is a diagram showing beamlet writing paths 611 for writing stripes 28 of a field 27 of a wafer. In this embodiment, multiple groups 621 of beamlets 610 are generated, each group of beamlets assigned to writing one stripe 28 of the field 27. In one embodiment, each beamlet group 621 is formed from a single sub-beam 510, and the sub-beams are arranged with writing paths 511 as shown in FIG. 5. Thus, in this arrangement, multiple sub-beams 510 are arranged with writing paths 511 evenly spaced and distributed in one direction (e.g. in the X-direction across the width of the field 27), and multiple beamlets 610 formed from each one of the sub-beams 510 are arranged with writing paths 611 evenly spaced and distributed in a different direction (e.g. in the Y-direction along the length of the field 27). The two directions are preferably exactly or nearly perpendicular to each other.

It should be noted that this arrangement may be used without actually forming any sub-beams. The groups of beamlets 610 may be formed in a single aperture array, in which the groups form beam spots 621 which are evenly spaced and distributed in one direction (e.g. in the X-direction across the width of the field 27). The multiple beamlets 610 in each group/beam spot 621 are arranged with writing paths 611 evenly spaced and distributed in a different direction (e.g. in the Y-direction along the length of the field 27), where the two directions are preferably exactly or nearly perpendicular to each other.

FIG. 11B is a diagram of an arrangement of beamlets 610 which may be generated by the aperture arrangement shown in FIG. 10A suitable for the writing scheme shown in FIG. 11A. The beamlets 610 are arranged to form writing paths 611 with uniform spacing 625 when the group of beamlets is scanned in the X-direction across the wafer. The writing paths 611 are evenly distributed across a beam spot width 610A in the Y-direction.

FIG. 12A is a simplified schematic diagram showing a beamlet crossover at the beam stop array 8. In particular, FIG. 12A shows a portion 6a of the multiple aperture array 6, a portion 8a of the beam stop array 8, and a portion 11a of the wafer. In each case, the portions 6a, 8a, and 11a correspond to a beamlet group, as shown in FIG. 10A.

To explain further, a beamlet group is projected from the multiple aperture array potion 6a and towards beam stop array portion 8a. The beamlet group crosses over at or near beam stop array portion. This crossover results in a translated image being projected on wafer portion 11a.

FIG. 12B shows in more detail the beamlet group translation. On the left, a group of beamlets 610 are shown, as exiting multiple aperture array portion 6a. The beamlets 610 are numbered in the same fashion as in FIG. 10A, but only the numbers 1, 7, 43, and 49 are shown for clarity. Further beamlet number 1 is shaded to clearly show the translation.

On the right, a group of beamlets 610′ are shown, as projected on wafer portion 11a. The two groups of beamlets 610 and 610′ show, for example, that beamlet numbers 1, 7, 43, and 49 are translated into a different position, along with the other beamlets not numbered in FIG. 12B.

FIG. 13A is an enlarged diagram, relative to FIG. 12B, showing the group of beamlets 610′, as projected on a wafer. FIG. 13B is a further enlarged diagram, showing a sub-group of four neighboring beamlets 610′. Because of focusing and demagnification, the column and row pitch may be much smaller in relation to the column and row pitch of the multiple aperture array portion shown in FIG. 10A. For example, in some embodiments the offset between beamlets neighboring within a row is 10.5 nm with a row and column pitch of 73.5 nm.

As further exampled below, one advantage of the present invention is minimizing overscan. FIG. 14 shows a schematic diagram of a scan line of a beam or beamlet, including the sub-beam or beamlet's overscan section. A beam deflector array (e.g., beam deflector array 9 of FIG. 1) generates a deflection signal, which includes a scan phase (from A to B) and a fly-back phase (from B to C). During the scan phase, the deflection signal moves a group of beamlets (corresponding to a sub-beam), each beam having its own scan line and scan area. After the scan phase, the fly-back phase starts, in which the beamlets are switched off and the deflection signal quickly moves the beamlets back to the position where the next scan phase will start.

A scan line is the path of a sub-beam or beamlet on the surface of the wafer during the scan phase. A scan line (see FIG. 14 at the right) is divided into three sections: a start overscan section, a pattern section, and an end overscan section. In the overscan sections, the beamlets are typically switched off. In the pattern section, the beamlets are switched on according to the features required to be written in the wafer field. The bits in the scan-line bit frame for both the overscan section and pattern section represent data to be transferred to the beam blanker array. The bits/pixels in the overscan section consume bandwidth of the data path and increase wafer processing time.

It is therefore desirable to arrange the apertures of the aperture plate to minimize overscanning. Embodiments of the present invention minimize this problem, as can be seen in FIGS. 15A and 15B.

FIGS. 15A and 15B are diagrams showing two groups of beamlets and their respective overscan length. Beamlet group 1100 is projected by an multiple aperture array in an embodiment of the present invention. Beamlet group 1120 is projected by an alternative multiple aperture array having a rotated balanced array. Both beamlet groups 1100 and 1120 are shown as projected on a section of a wafer. Both beamlet groups have the same number of beamlets and are projected by multiple aperture arrays that have the same fill factor and a column and row pitch of 8 μm.

As explained in FIG. 14, a scanline bit frame includes two overscan sections, a start overscan section and end overscan section. For some writing schemes, the bit length of these sections are in proportion to the X-axis width of a beamlet group. Beamlet group 1120 is 63 nm wider than beamlet group 1100. The overscan per scan line for beamlet group 1120 is 1.104 μm compared to 1.041 μm for beamlet group 1100. Further, the throughput performance of beamlet group 1100 is at least 2% higher than beamlet group 1120.

Although the figures show a particular lithography system, sub-beam array 4 and multiple aperture array 6 are beneficial in a number of different configurations upstream and downstream of the arrays, including the use of either array 4 or 6 individually and with other arrays not within the scope of the invention. Arrays 4 and 6 may be implemented in either parallel or perpendicular writing strategies. Further, the beamlets may be focused individually or in groups.

Thus, it will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention, which is defined in the accompanying claims.

Claims

1. A sub-beam aperture array for forming a plurality of sub-beams from one or more charged particle beams, the sub-beam aperture array comprising one or more beam areas, each beam area comprising a plurality of sub-beam apertures arranged in columns in a non-regular hexagonal pattern of neighboring sub-beam apertures, the sub-beam apertures arranged so that, when projected in a first direction onto a line parallel to a second direction, the sub-beam apertures in each column are uniformly spaced along the line, and wherein the first direction is different from the second direction,

wherein, within each of the one or more beam areas, the sub-beam apertures in each column are staggered, in the first direction, with respect to the sub-beam apertures of a neighboring column, and

wherein the sub-beam apertures of every other column are aligned in the second direction.

2. The sub-beam aperture array of claim 1, wherein, within each of the one or more beam areas, the sub-beam apertures are arranged in a plurality of columns regularly spaced in the second direction, and the sub-beam apertures in each column are offset by a same amount, in the second direction, from each adjacent sub-beam aperture in the same column.

3. The sub-beam aperture array of claim 2, wherein the offset between sub-beam apertures within each column is the same as an offset between a sub-beam aperture in one beam area and an adjacent sub-beam aperture in a corresponding column of another beam area.

4. The sub-beam aperture array of claim 3, wherein the offset of adjacent sub-beam apertures in a single column is equal to a fraction of a diameter of the sub- beam apertures.

5. The sub-beam aperture array of claim 1, wherein, within each of the one or more beam areas, the sub-beam apertures in each column are staggered, in the first direction, with respect to the sub-beam apertures of a neighboring column.

6. The sub-beam aperture array of claim 1, wherein the sub-beam apertures of every other column are aligned in the second direction.

7. The sub-beam aperture array of claim 1, wherein the second direction is substantially perpendicular to the first direction.

8. A charged particle lithography system for exposing a target using a plurality of charged particle sub-beams, the system comprising:

a charged particle generator for generating a charged particle beam;

a sub-beam aperture array for forming a plurality of sub-beams from one or more the charged particle beams beam, the sub-beam aperture array comprising one or more beam areas, each beam area comprising a plurality of sub-beam apertures arranged in columns in a non-regular hexagonal pattern of neighboring sub-beam apertures, the sub-beam apertures arranged so that, when projected in a first direction onto a line parallel to a second direction, the sub-beam apertures in each column are uniformly spaced along the line, and wherein the first direction is different from the second direction; and

a projection lens system configured to project the sub-beams onto a surface of the target;

wherein the system further comprises a beamlet aperture array comprising a plurality of beamlet apertures arranged in one or more groups, the beamlet aperture array arranged to receive the sub-beams and form a plurality of beamlets at the locations of the beamlet apertures of the beamlet array,

wherein the sub-beam apertures in each column are staggered, in the first direction, with respect to the sub-beam apertures of a neighboring column, and

wherein the sub-beam apertures of every other column are aligned in the second direction.

9. The system of claim 8, further comprising a beamlet aperture array comprising a plurality of beamlet apertures arranged in one or more groups and arranged to receive the sub-beams, and wherein each group of beamlet apertures corresponds with a separate charged particle sub-beam projected onto the beamlet aperture array.

10. The system of claim 8, further comprising a beamlet aperture array comprising a plurality of beamlet apertures arranged in one or more groups and arranged to receive the sub-beams, and wherein the beamlet apertures are arranged so that, when projected in a fourth direction onto a line parallel to a third direction, the sub-beam beamlet apertures of each group are uniformly spaced along the line, and wherein the third direction is different from the fourth direction.

11. The system of claim 10, wherein the first direction is the same as the third direction, and the second direction is the same as the fourth direction.

12. The system of claim 10, wherein the beamlet apertures are arranged in rows and columns, and each beamlet aperture within a row of the beamlet aperture array is uniformly offset in the third direction from adjacent beamlet apertures in the row.

13. The system of claim 10, wherein the beamlet apertures within a column of each group align in the fourth direction.

14. The system of claim 8, further comprising a beamlet aperture array comprising a plurality of beamlet apertures and arranged to receive the sub-beams, and wherein the beamlet apertures are arranged in a plurality of groups, each group corresponding to a sub-beam, wherein the positions of the beamlet apertures within each group positioned to form an unbalanced array.

15. The system of claim 14, wherein beamlet apertures neighboring within a row of the beamlet aperture array are offset from each other by a uniform amount with respect to the a third direction.

16. The system of claim 15, wherein the offset is equal to a fraction of the pitch between the neighboring beamlet apertures.

17. The system of claim 16, wherein the fraction is equal to the pitch between the neighboring beamlet apertures divided by the number of beamlet apertures within the row.

18. The system of claim 8, further comprising:

a beamlet aperture array comprising a plurality of beamlet apertures arranged to receive the sub-beams and to form a plurality of beamlets at the locations of the beamlet apertures of the beamlet aperture array,

wherein the beamlet apertures in each group form a skewed square array.

19. The system of claim 8, further comprising a beamlet aperture array comprising a plurality of beamlet apertures and arranged to receive the sub-beams, and wherein the plurality of beamlet apertures in each group are all offset from the center of a beam spot formed by the group of beamlet apertures.

20. The system of claim 19, wherein forty-nine beamlet apertures are arranged within the beam spot, each beamlet aperture is associated with an aperture number, and the offset in an X direction of each beamlet aperture from the center of the beam spot is defined by the formula: appxoffset=(int[(aperture number−1)/7)]−3)*pitch, where int is a floor function.

21. The system of claim 19, wherein the offset in a Y direction of each beamlet aperture from the center of the beam spot is defined by the formula: appyoffset =(−pitch/2)+[(6−[(aperture number−1) mod 7]+int(aperture number/29)−3)*pitch]−[(pitch/7)*(int[(aperture number−1)/7)]−3)], where int is a floor function.

22. The system of claim 8, further comprising a deflector arranged to deflect the sub-beams in the first direction and a moveable stage for moving the target in the second direction.

23. A beamlet aperture array for forming a plurality of beamlets from charged particle sub-beams, the beamlet aperture array comprising consisting of a plurality of beamlet apertures arranged in a plurality of groups, each group corresponding to a sub-beam, wherein the plurality of groups are arranged in a non-regular hexagonal pattern of neighboring groups and wherein the positions of the beamlet apertures within each group form an unbalanced array.

24. The beamlet aperture array of claim 23, wherein beamlet apertures neighboring within a row of the beamlet aperture array are offset from each other by a uniform amount with respect to a third direction.

25. The beamlet aperture array of claim 24, wherein the offset is equal to a fraction of the pitch between the neighboring beamlet apertures.

26. The beamlet aperture array of claim 25, wherein the fraction is equal to the pitch between the neighboring beamlet apertures divided by the number of beamlet apertures within the row.

27. The beamlet aperture array of claim 23, wherein the beamlet apertures in each group form a skewed square array.

28. The beamlet aperture array of claim 23, wherein the beamlet apertures in each group are all offset from the center of a beam spot formed by the group of beamlet apertures.

29. The beamlet aperture array of claim 28, wherein forty-nine beamlet apertures are arranged within the beam spot, each beamlet aperture is associated with an aperture number, and the offset in an X direction of each beamlet aperture from the center of the beam spot is defined by the formula: appxoffset=(int[(aperture number−1)/7)]−3)*pitch, where int is a floor function.

30. The beamlet aperture array of claim 28, wherein the offset in a Y direction of each beamlet aperture from the center of the beam spot is defined by the formula: appyoffset=(−pitch/2)+[(6−[(aperture number−1)mod 7]+int(aperture number/29)−3)*pitch]−[(pitch/7)*(int[(aperture number−1)/7)]3)], where int is a floor function.

31. The beamlet aperture array of claim 23, wherein the groups are arranged in a non-regular hexagonal array.

32. The beamlet aperture array of claim 23, further comprising one or more beam areas, each beam area comprising a plurality of groups of beamlet apertures, wherein in each beam area the groups are arranged in a non-regular hexagonal array.

33. A method for exposing a field of a target using a plurality of charged particle beamlets, the field having a length in a first direction and a width in a second direction, the method comprising:

forming the charged particle beamlets into a plurality of discrete groups arranged in columns in a non-regular hexagonal pattern of neighboring discrete groups, the groups being equally spaced across the width of the field; and moving the target in the first direction and simultaneously scanning each group of beamlets across a width of a corresponding stripe of the field so that each beamlet follows a writing path on a surface of the target; wherein the writing paths of the beamlets of each group in each column are evenly spaced in the first direction,

wherein the plurality of discrete groups arranged such that discrete groups in each column are staggered, in the first direction, with respect to the discrete groups of a neighboring column, and

wherein the discrete groups of every other column are aligned in the second direction.

34. The method of claim 33, wherein the discrete groups are arranged in a plurality of columns regularly spaced in the second direction, and the discrete groups in each column are offset by a same amount, in the second direction, from each adjacent discrete group in the same column.