Raster shaped beam, electron beam exposure strategy using a two dimensional multipixel flash field

• US 6,262,429 B1
• Filed: 01/06/1999
• Issued: 07/17/2001
• Est. Priority Date: 01/06/1999
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: ETEC Systems Incorporated (Applied Materials Incorporated)
• Inventors: Varner, Jeffery K., Wang, Weidong, Sagle, Allan L., Veneklasen, Lee H., Rishton, Stephen A.
• Primary Examiner(s): Arroyo, Teresa M.
• Assistant Examiner(s): Wells, Nikita
• Application Number:
  US09/226,361
• Time in Patent Office: 923 Days
• Field of Search: 250/492.23, 250/492.22, 250/492.2
• US Class Current: 250/492.23
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: H01J 2237/30488 Raster scan
• CPC Class Codes: H01J 2237/31776 Shaped beam
• CPC Class Codes: H01J 37/3026 Patterning strategy
• CPC Class Codes: H01J 37/3174 Particle-beam lithography, e.g. electron beam lithography

Abstract

An electron beam column (or other charged particle beam column) for lithography which exposes a surface to variable shapes in a raster scan. The beam column includes an electron (or ion) source that generates a charged particle beam, a transfer lens, an upper aperture, an upper deflector, a lower aperture, a lower deflector, magnetic deflection coils, and a beam objective lens. The beam is first shaped as a square in cross section by the upper aperture. The upper deflector changes the direction of the square shaped beam to pass through a specific portion of an opening defined in the lower aperture to shape the beam as desired. The lower aperture defines either a cross shaped opening or four L-shaped openings arranged as corners of a square. The combination of upper and lower apertures enable definition of exterior and interior corners as well as horizontal and vertical edges of a pattern, so that only one flash need be exposed in any one location on the surface. The lower deflector reverses any change in direction imposed by the upper deflector and further applies a retrograde scan to counteract a movement of the beam by the magnetic coils in a raster scan. The retrograde scan ensures that an exposure exposes an intended target area.

Claims

1. A charged particle beam column for writing variable shaped beams onto a surface, comprising:

a source of a charged particle beam;

a transfer lens positioned downstream of said source;

a first aperture element coaxial with said beam and positioned downstream of said source and that defines an opening;

a first deflector coaxial with said beam and positioned downstream of said first aperture element, and which generates an electric field;

a second aperture element coaxial with said beam and positioned downstream of said first deflector and defining at least one opening, wherein said electric field directs said beam onto said at least one opening thereby to variably shape said beam, said at least one opening comprising at least one of one or more substantially L-shaped openings or cross-shaped openings;

a second deflector coaxial with said beam and positioned downstream of said second aperture element, and which generates a second electric field;

magnetic coil deflectors positioned downstream of said second deflector thereby to raster scan said beam; and

an objective lens, wherein said objective lens focuses said variably shaped beam onto said surface and controls a final size of said variably shaped beam on said surface.

2. The charged particle beam column of claim 1, wherein said transfer lens focuses said charged particle beam at a crossover point near but not within a same plane as said second aperture element, wherein a distance between said crossover point and said first aperture is more than twice a second distance between said crossover point and said second aperture.

3. The charged particle beam column of claim 2, wherein a portion of said charged particle beam that traverses said at least one opening of said second aperture element forms a shadow in a site plane, wherein a third distance from said site plane to said crossover point is less than a fourth distance from said second aperture element to said crossover point.

4. The charged particle beam column of claim 3, wherein said objective lens focuses said shadow in said site plane onto said surface.

5. The beam column of claim 1 wherein said opening in said first aperture element is square shaped.

6. The beam column of claim 1 wherein said at least one opening comprises four openings, each of said four openings being L shaped and wherein said four openings are arranged as corners of a square.

7. The beam column of claim 1 wherein said at least one opening is cross shaped.

8. The beam column of claim 1 wherein said source is a thermal field emission electron source.

9. The beam column of claim 1 wherein said second electric field of said second deflector changes a direction of said beam such that said beam appears to emanate from a plane downstream from said second aperture element.

10. The beam column of claim 1 wherein said second electric field of said second deflector directs said beam in a retrograde scan.

11. The beam column of claim 1 wherein said electric field of said first deflector changes a direction of said beam such that said beam intersects a solid portion of said second aperture element thereby blanking said beam.

12. The beam column of claim 1 wherein said first deflector comprises:

first, second, third, and fourth plates arranged in a square configuration;

a first voltage source which couples a first voltage across said first and third plates, wherein said first and third plates face one another; and

a second voltage source which couples a second voltage across said second and fourth plates, wherein said second and fourth plates face one another.

13. The beam column of claim 12 wherein said second deflector comprises:

fifth, sixth, seventh, and eighth plates arranged in a square formation;

a third voltage source which couples a third voltage across said fifth and seventh plates, wherein said fifth and seventh plates face one another; and

a fourth voltage source which couples a fourth voltage across said sixth and eighth plates, wherein said sixth and eighth plates face one another.

14. The beam column of claim 13 wherein said first, second, third, and fourth voltage sources together comprise:

a translator which outputs first, second, third, and fourth values;

a retrograde scan circuit that outputs a retrograde signal;

an output circuit coupled to receive said first, second, third, and fourth values and said retrograde signal, wherein said output circuit adjusts said fourth value according to said retrograde signal and outputs said first, second, third, and fourth voltages; and

a timer circuit that controls a duration said output circuit outputs said first and second voltages.

15. The beam column of claim 14, wherein said translator comprises:

a first memory which stores said first value and said second value, both associated with said variable shape; and

a second memory which stores said third value and said fourth value.

16. A method for shaping a charged particle beam, comprising:

generating said charged particle beam;

shaping said beam through a first opening;

deflecting said shaped beam through a second opening spaced apart from said first opening, said at least one opening comprising at least one of one or more substantially L-shaped openings or cross-shaped openings, thereby further shaping said beam; and

deflecting said further shaped beam in a raster scan.

17. The method of claim 16, wherein said shaping further comprises:

directing said beam on said first opening; and

generating a shadow of said first opening.

18. The method of claim 17, wherein said deflecting said shaped beam through a second opening further comprises:

directing said shadow on said second opening;

generating a second shadow of a portion said shadow that traverses said second opening in a site plane.

19. The method of claim 18 further comprising imaging said second shadow in said site plane on a surface.

20. The method of claim 16 wherein said second opening is one of four openings, each opening being L-shaped and arranged as corners of a square.

21. The method of claim 16 wherein said second opening is cross shaped.

22. The method of claim 16 further comprising raster scanning said beam.

23. The method of claim 16 wherein said deflecting further comprises deflecting said shaped beam to intersect a solid surface of said aperture element thereby to blank said beam.

24. An apparatus to write flash fields on a substrate in a raster scan, said flash fields defining a pattern, comprising:

a rasterizer which rasterizes a surface of said substrate into pixels and outputs gray level values, wherein said gray level values specify a proportion of a pixel that overlaps with said pattern;

a buffer coupled to receive and store said gray level values from said rasterizer;

a flash converter coupled to receive said gray level values from said buffer, wherein said flash converter outputs shape data that define a flash field;

a dose value circuitry coupled to said rasterizer, wherein said dose value circuitry computes dose values associated with said shape data;

a converter coupled to receive said shape data from said flash converter and associated dose values from said dose value circuitry, wherein said converter outputs signals that specify a shape of said flash field, duration of said flash field, and a position of said flash field on said substrate; and

a charged particle beam column coupled to receive said signals from said converter, and which generates said flash field as specified by said signals from said converter.

25. The apparatus of claim 24 wherein said flash converter and said dose value circuitry output said shape data and said dose values to said converter in said raster scan.

26. The apparatus of claim 25 wherein said beam column generates said flash fields in said raster scan.

29. An apparatus as recited in claim 24, wherein said shape data comprises a shape code representing a basic shape and shape coordinates modifying said basic shape.

30. An apparatus as recited in claim 24, said shape data representative of one or more L-shaped areas.

27. A method of calculating and generating flash fields to be written onto a substrate comprising:

representing said substrate as a grid of pixels;

representing each said pixel as a gray level value that specifies a proportion of each said pixel that is to be exposed by a charged particle beam;

determining, from said gray level values, shape data that define a flash field;

determining dose values associated with said shape data;

specifying a shape of said flash field, duration of said flash field, and a position of said flash field on said substrate; and

generating said flash field, responsive to said specifying.

28. A method for manufacturing an apparatus to write flash fields on a substrate in a raster scan, said flash fields defining a pattern, comprising:

providing a rasterizer which rasterizes a surface of said substrate into pixels and outputs gray level values, wherein said gray level values specify a proportion of a pixel that overlaps with said pattern;

providing a buffer coupled to receive and store said gray level values from said rasterizer;

providing a flash converter coupled to receive said gray level values from said buffer, wherein said flash converter outputs shape data that define a flash field;

providing a dose value circuitry coupled to said rasterizer, wherein said dose value circuitry computes dose values associated with said shape data;

providing a converter coupled to receive said shape data from said flash converter and associated dose values from said dose value circuitry, wherein said converter outputs signals that specify a shape of said flash field, duration of said flash field, and a position of said flash field on said substrate; and

providing a charged particle beam column coupled to receive said signals from said converter, and which generates said flash field as specified by said signals from said converter.