Charged particle beam exposure system and method of exposing a pattern on an object by such a charged particle beam exposure system

• US 5,391,886 A
• Filed: 10/05/1993
• Issued: 02/21/1995
• Est. Priority Date: 08/09/1991
• Status: Expired due to Term

• Current Assignee: Fujitsu Semiconductor Limited (Fujitsu Limited)
• Original Assignee: Fujitsu Limited
• Inventors: Hatta, Junko, Yamazaki, Satoru, Kobayashi, Katsuhiko, Yamada, Akio, Oae, Yoshihisa, Abe, Tomohiko, Sakamoto, Kiichi
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US08/131,670
• Time in Patent Office: 504 Days
• Field of Search: 250/492.22, 250/492.2 R, 250/398, 250/252.1 R
• US Class Current: 250/492.22
• 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 37/3174 Particle-beam lithography, e.g. electron beam lithography

Abstract

A method of exposing a pattern on a substrate by a charged particle beam includes the steps of energizing first and second mask deflectors provided at an upstream side of a stencil mask simultaneously to obtain a first relativistic relationship of energization between the first and second mask deflectors, energizing the first mask deflector and simultaneously the second mask deflector according to the first relativistic relationship so as to hit a selected aperture on the stencil mask, to obtain an absolute deflection of the charged particle beam as a function of the energization of the first mask deflector, energizing third and fourth mask deflectors provided at a downstream side of the stencil mask simultaneously to obtain a second relativistic relationship of energization between the third and fourth mask deflectors, and energizing the first through fourth mask deflectors according to the first and second relativistic relationship and further to the absolute relationship, such that the charged particle beam is deflected away from an optical axis and hit a selected aperture on the stencil mask while traveling parallel to the optical axis, and such that the charged particle beam passed through the stencil mask is deflected toward the optical axis and deflected again such that the charged particle beam travels toward the substrate in alignment with the optical axis.

Claims

1. A method for exposing a pattern on an object by means of a focused charged particle beam, comprising the steps of:

forming a charged particle beam in a beam source such that said charged particle beam travels toward said object along an optical axis;

focusing said charged particle beam upon said object;

shaping said charged particle beam in a region between said beam source and said object to form a shaped charged particle beam, said step of shaping comprising a step of deflecting said charged particle beam away from said optical axis by energizing deflection means that includes a plurality of deflectors, such that said charged particle beam passes one of a plurality of apertures provided on a beam shaping mask;

deflecting back said shaped charged particle beam again upon said optical axis;

radiating said shaped charged particle beam along said optical axis upon a shielding plate that is formed with a pinhole having a size generally corresponding to a diameter of said charged particle beam, said shielding plate being provided on said optical axis at a location between said beam shaping mask and said object; and

selectively causing a turning off of said charged particle beam on said object by selectively deflecting said charged particle beam that has been radiated upon said shielding plate, away from said pinhole, said plurality of deflectors including first through fourth deflectors wherein said first and second deflectors are disposed at a side close to said beam source with respect to said beam shaping mask and such that said third and fourth deflectors are disposed at a side close to said object;

said method further comprising the steps of;

(a-1) energizing said first deflector forming said deflection means to cause a deflection of said charged particle beam to a plurality of calibration points that are located offset from said optical axis; and

energizing, in each of said calibration points, the remaining deflectors forming said deflection means;

(a-2) detecting an intensity of said charged particle beam arriving at said object while energizing said remaining deflectors in said step (a-1), for each of said calibration points; and

obtaining optimized energization of said remaining deflectors by optimizing energization of said remaining deflectors such that the charged particle beam, deflected in said step (a-1) and arriving at said object after passing through said pinhole, has a maximum intensity;

(a-3) obtaining a relativistic correction function that describes said optimized energization of said remaining deflectors obtained in said step (a-2) as a function of the energization of said first deflector;

(a-4) energizing said first deflector to cause a deflection of said charged particle beam such that said charged particle beam passes a selected aperture on said beam shaping mask;

energizing said remaining deflectors according to said relativistic correction function, simultaneously to said first deflector that is deflecting said charged particle beam to said selected aperture; and

obtaining optimized energization of said first deflector such that said charged particle beam, arriving at said object after passing through said pinhole, has a maximum intensity;

(a-5) obtaining an absolute correction function that describes said optimized energization of said first deflector obtained in said step (a-4), as a function of a position of said selected aperture on said beam shaping mask; and

(b) deflecting said charged particle beam by energizing said first deflector according to said absolute correction function and said remaining deflectors according to said relativistic correction function, based upon energization of said first deflector, such that said electron beam hits said selected aperture on said beam shaping mask;

said step (a-2) further comprising the steps of;

(a-2-1) obtaining optimized energization of said second deflector with respect to energization of said first deflector by energizing said first and second deflectors simultaneously, such that said charged particle beam arriving at said object has a maximum intensity; and

(a-2-2) obtaining optimized energization of said third deflector with respect to the energization of said fourth deflector by energizing said third and fourth deflectors simultaneously, such that said charged particle beam arriving at said object has a maximum intensity.

2. A method as claimed in claim 1, wherein said step (a-3) comprises a step of obtaining a first relativistic correction function based upon said optimized energization of said second deflector obtained in said step (a-2-1), said first relativistic correction function describing a relationship between said optimized energization of said second deflector and the energization said first deflector.

3. A method as claimed in claim 2, wherein said step (a-3) comprises a step of obtaining a second relativistic correction function based upon said optimized energization of said third deflector obtained in said step (a-2-2), said second relativistic correction function describing a relationship between said optimized energization of said third deflector and the energization of said fourth deflector.

4. A method as claimed in claim 2, wherein said step (a-3) comprises a step of obtaining third and fourth relativistic correction functions respectively representing said optimized energization of said third and fourth deflectors with respect to the energization of said first deflector, by energizing said first through fourth deflectors simultaneously such that said charged particle beam arriving at said object after passing through said pinhole has a maximum intensity on said object.

5. A method as claimed in claim 1, wherein said relativistic correction function represents the relationship between the energization of said first deflector and the optimized energization of said remaining deflectors by a polynomial.

6. A method for exposing a pattern on an object by means of a focused charged particle beam, comprising the steps of:

forming a charged particle beam in a beam source such that said charged particle beam travels toward said object along an optical axis;

focusing said charged particle beam upon said object;

shaping said charged particle beam in a region between said beam source and said object to form a shaped charged particle beam, said step of shaping comprising a step of deflecting said charged particle beam away from said optical axis by energizing deflection means that includes a plurality of deflectors, such that said charged particle beam passes one of a plurality of apertures provided on a beam shaping mask;

deflecting back said shaped charged particle beam again upon said optical axis;

radiating said shaped charged particle beam along said optical axis upon a shielding plate that is formed with a pinhole having a size generally corresponding to a diameter of said charged particle beam, said shielding plate being provided on said optical axis at a location between said beam shaping mask and said object; and

selectively causing a turning off of said charged particle beam on said object by selectively deflecting said charged particle beam that has been radiated upon said shielding plate, away from said pinhole;

said method further comprising the steps of;

(a-1) energizing a first deflector forming said deflection means to cause a deflection of said charged particle beam to a plurality of calibration points that are located offset from said optical axis; and

energizing, in each of said calibration points, the remaining deflectors forming said deflection means;

(a-2) detecting an intensity of said charged particle beam arriving at said object while energizing said remaining deflectors in said step (a-1), for each of said calibration points; and

obtaining optimized energization of said remaining deflectors by optimizing energization of said remaining deflectors such that the charged particle beam, deflected in said step (a-1) and arriving at said object after passing through said pinhole, becomes maximum;

(a-3) obtaining a relativistic correction function that describes said optimized energization of said remaining deflectors obtained in said step (a-2) as a function of the energization of said first deflector;

(a-4) energizing said first deflector to cause a deflection of said charged particle beam such that said charged particle beam passes a selected aperture on said beam shaping mask;

energizing said remaining deflectors according to said relativistic correction function, simultaneously to said first deflector that is deflecting said charged particle beam to said selected aperture; and

obtaining optimized energization of said first deflector such that said charged particle beam, arriving at said object after passing through said pinhole, has a maximum intensity;

(a-5) obtaining an absolute correction function that describes said optimized energization of said first deflector obtained in said step (a-4), as a function of a position of said selected aperture on said beam shaping mask;

(b-1) energizing said first deflector and simultaneously an astigmatic compensation coil provided along said optical axis at a side close to said beam source with respect to said shielding plate, said astigmatic compensation coil compensating for astigmatism upon energization;

(b-2) obtaining optimized energization of said astigmatic compensation coil, by optimizing said energization of said astigmatic compensation coil such that said charged particle beam has a maximum intensity on said object, while simultaneously detecting said intensity of said charged particle beam on said object;

(b-3) obtaining an astigmatic correction function describing said optimized energization of said astigmatic compensation coil as a function of the energization of said first deflector;

(c-1) energizing said first deflector and simultaneously a focusing compensation coil provided along said optical axis at a side close to said beam source with respect to said shielding plate, said focusing compensation coil adjusting a focal point of said charged particle beam;

(c-2) obtaining optimized energization of said focusing compensation coil, by optimizing said energization of said focusing compensation coil such that said charged particle beam has a maximum intensity on said object, while simultaneously detecting said intensity of said charged particle beam on said object;

(c-3) obtaining a focusing correction function describing said optimized energization of said focusing compensation coil as a function of the energization of said first deflector; and

(d) deflecting said charged particle beam to hit said selected aperture on said beam shaping mask by energizing said deflectors of the deflection means, said astigmatic compensation coil, and said focusing correction coil according to said absolute correction function, said relativistic correction function, said astigmatic correction function, and said focusing correction function respectively, based upon the energization of said first deflector such that said charged particle beam is shaped by said selected aperture.

7. A method as claimed in claim 6, wherein said steps (b-1) and (b-2) and said steps (c-1) and (c-2) are carried out after said steps (a-1) and (a-2) are carried out.

8. A method as claimed in claim 6, wherein said steps (b-1) and (b-2) are carried out after said steps (c-1) and (c-2) are carried out.

9. A method as claimed in claim 6, wherein said steps (c-1) and (c-2) are carried out after said steps (b-1) and (b-2) are carried out.

10. A method as claimed in claim 6, wherein said relativistic correction function represents the energization of said first deflector and the optimized energization of the remaining deflectors by a first polynomial.

11. A method as claimed in claim 10, wherein said focusing correction function represents the energization of said first deflector and the optimized energization of said focusing compensation coil by a second polynomial having an order identical with an order of said first polynomial that described said relativistic correction function.

12. A method as claimed in claim 10, wherein said astigmatic correction function represents the energization of said first deflector and the optimized energization of said astigmatic compensation coil by a third polynomial having an order identical with an order of said first polynomial.

13. A method as claimed in claim 6, wherein, in each of said steps (a-2), (a-4), (b-2) and (c-2), said intensity of said charged particle beam on said object is represented by a parabolic function of said driving energy, and wherein each of said steps (a-2), (a-4), (b-2) and (c-2) comprises a step of obtaining said optimized energization as the energization that maximizes said intensity.

14. A method as claimed in claim 13, wherein each of said steps (a-2), (a-4), (b-2) and (c-2) comprises the steps of searching said optimized energization in a search range, and searching said optimized energization again while shifting said search range in the event said optimized energization is not included in said search range.

15. A method as claimed in claim 14, wherein said step of searching said optimized energization is repeated until said optimized energy is located substantially at the center of said search range.

16. A method as claimed in claim 6, wherein said step (d) further comprises the steps of detecting an intensity of said charged particle beam arriving at said object, and updating lower order coefficients of said relativistic correction function and said absolute correction function by carrying out said steps (a-1)-(a-5) in the event that said intensity has decreased below a predetermined intensity, while leaving higher order coefficients of said relativistic correction function and said absolute correction function unchanged.

17. A method as claimed in claim 16, wherein said step (d) further comprises the steps of forming updated relativistic correction function and updated absolute correction function, based upon said lower order coefficients updated in said updating step and further based upon said higher order coefficients that remain unchanged, and energizing said first deflectors and said remaining deflectors by said updated relativistic correction function and said updated absolute correction function.

18. A charged particle exposure system for exposing a pattern on an object, comprising:

beam source means for producing a charged particle beam and emitting the same toward said object along an optical axis;

focusing means provided on said optical axis for focusing said charged particle beam upon said object;

a beam shaping mask provided on said optical axis between said object and said beam source means, said beam shaping mask carrying a plurality of apertures for shaping said charged particle beam;

beam deflection/shaping means provided along said optical axis between said object and said beam source means for deflecting said charged particle beam away from said optical axis such that said charged particle beam passes a selected aperture on said beam shaping mask;

a beam interruption plate provided on said optical axis between said object and said beam shaping mask for interrupting said charged particle beam, said beam interruption plate having a pinhole in correspondence to said optical axis for passing said charged particle beam;

deflection means provided along said optical axis between said beam source means and beam interruption plate, for selectively causing an offset in said charged particle beam away from said optical axis upon energization, for causing a turning on and turning off of said charged particle beam on said object;

astigmatic correction means provided along said optical axis between said beam interruption plate and said beam source means, for compensating for astigmatism of said charged particle beam when said charged particle beam is deflected away from said optical axis; and

focusing correction means provided along said optical axis between said beam interruption plate and said beam source means, for adjusting a focal point of said charged particle beam such that said focal point coincides to said beam interruption means when said charged particle beam is deflected away from said optical axis;

wherein said charged particle beam exposure system further comprises;

pattern selection means supplied with exposure data corresponding to a pattern to be exposed on said object, for producing a positional selection signal that specifies the position of said selected aperture on said beam shaping mask;

deflection signal outputting means supplied with said positional selection signal from said pattern selection means for producing a first driving signal for energizing said deflection/shaping means;

astigmatic correction signal outputting means supplied with said first driving signal from said deflection signal outputting means for producing a second driving signal for energizing said astigmatic correction means; and

focusing correction signal outputting means supplied with said first driving signal from said deflection signal outputting means for producing a third driving signal for energizing said focusing correction means;

wherein said deflection signal outputting means storing therein a first function for converting said positional selection signal to said first driving signal for driving said deflection/shaping means;

said astigmatic correction signal outputting means storing therein a second function for converting said positional selection signal to said second driving signal; and

said focusing correction signal outputting means storing therein a third function for converting said positional selection signal to said third driving signal.