Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-07-31
2002-01-08
Anderson, Bruce (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S398000
Reexamination Certificate
active
06337485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron beam exposure apparatus and, more particularly, to an electron beam exposure apparatus for drawing a pattern on a wafer or drawing a pattern on a mask or reticle using a plurality of electron beams, and its control method.
2. Description of the Related Art
An electron beam exposure apparatus includes a point beam type apparatus which uses a beam shaped in a spot pattern, a variable rectangular beam type apparatus which uses a beam shaped to have a rectangular section with a variable size, a stencil mask type apparatus which shapes a beam into a desired sectional shape using a stencil, and the like.
The point beam type electron beam exposure apparatus is used for only research purposes due to its low throughput. The variable rectangular beam type electron beam exposure apparatus has a throughput higher by one or two orders of magnitude than that of the point beam type, but suffers problems in terms of throughput when highly integrated patterns having a line width as small as about 0.1 &mgr;m are to be formed by exposure. On the other hand, the stencil mask type electron beam exposure apparatus uses a stencil mask formed with a plurality of repetitive pattern through holes in a portion corresponding to a variable rectangular aperture. Hence, the stencil mask type electron beam exposure apparatus is effective for exposure of repetitive patterns. However, when a semiconductor circuit requires a large number of transfer patterns that cannot be formed on a single stencil mask, a plurality of stencil masks must be prepared in advance, and must be used one by one, resulting in a long mask exchange time and a considerable throughput drop.
As an apparatus that can solve the above problems, a multi-electron beam type exposure apparatus is known. In this apparatus, a plurality of electron beams are irradiated on the sample surface along the course of design coordinate positions, and are deflected along that course of design coordinate positions to scan the sample surface. In addition, the plurality of electron beams are individually ON/OFF-controlled in correspondence with the pattern to be drawn, thereby drawing the pattern. Since the multi-electron beam type exposure apparatus can draw an arbitrary pattern, it can improve the throughput.
FIG. 15A
schematically shows the multi-electron beam type exposure apparatus. Reference numerals
501
a
,
501
b
, and
501
c
denote electron guns that can individually ON/OFF-control electron beams. Reference numeral
502
denotes a reduction electron optical system for projecting a plurality of electron beams emitted by the electron guns
501
a
,
501
b
, and
501
c
onto a wafer
503
in a reduced scale; and
504
, a deflector for deflecting the plurality of electron beams to be projected onto the wafer
503
in the reduced scale.
The plurality of electron beams coming from the electron guns
501
a
,
501
b
, and
501
c
are deflected by an identical amount by the deflector
504
. With this deflection, the respective electron beams are deflected while sequentially settling their positions on the wafer in accordance with a matrix having a matrix spacing defined by the minimum deflection width of the deflector
504
with reference to their beam reference positions. The individual electron beams form exposure patterns on different exposure regions by exposure.
FIGS. 15B
to
15
D show the state wherein the electron beams coming from the electron guns
501
a
,
501
b
, and
501
c
expose the corresponding exposure regions to form exposure patterns in accordance with an identical matrix. The respective electron beams move while settling their positions on the matrix at the same time like (1, 1), (1, 2), . . . , (1, 16), (2, 1), (2, 2), . . . , (2, 16), (3, 1), . . . , and expose the corresponding regions to form patterns (P
1
, P
2
, P
3
) by turning on the beams at the positions of the exposure patterns (P
1
, P
2
, P
3
).
In the multi-electron beam type exposure apparatus, since the respective beams simultaneously form different patterns, the size of each electron beam and the minimum deflection width of the deflector
504
corresponding to that size are set in correspondence with the minimum line width of the exposure patterns. As the minimum line width becomes smaller, the number of times of exposure while settling the electron beam positions increases, resulting in a considerable throughput drop.
The exposure patterns do not always equally include patterns with a minimum line width. However, conventionally, even in a region defined by a pattern having a line width larger than the minimum line width, exposure is done using the electron beam size and the minimum deflection width corresponding to that size, determined based on the minimum line width in all the patterns. For this reason, the throughput drops as the minimum line width of the pattern shrinks.
SUMMARY OF THE INVENTION
It is an object of the present invention to achieve high throughput by dynamically changing the dot pattern size to be formed on the object to be exposed upon forming a single pattern by exposure.
An electron beam exposure apparatus according to one aspect of the present invention is an electron beam exposure apparatus for drawing a pattern on an object to be exposed using a plurality of electron beams, comprising an electron source for emitting electrons, a plurality of elementary electron optical systems for respectively forming intermediate images of the electron source, a projection electron optical system for projecting the plurality of intermediate images onto the object to be exposed and an adjustment unit for dynamically adjusting sizes of dot patterns formed on the object to be exposed upon projection of the intermediate images in correspondence with fields to be exposed of the pattern to be drawn by exposure on the object to be exposed.
In the electron beam exposure apparatus, the adjustment unit dynamically adjusts the sizes of the intermediate images to be projected onto the object to be exposed, thereby dynamically adjusting the sizes of the dot patterns to be formed on the object to be exposed.
The electron beam exposure apparatus further comprises an illumination electron optical system which is inserted between the electron source and the plurality of elementary electron optical systems, and is adapted to convert the electrons emitted by the electron source into substantially collimated electron beams, and to irradiate the electron beams onto the plurality of elementary electron optical systems, and wherein the adjustment unit adjusts the focal length of the illumination electron optical system to adjust the sizes of the intermediate images to be projected onto the object to be exposed.
In the electron beam exposure apparatus, the adjustment unit adjusts the focal length of the illumination optical system while fixing a focal point position of the illumination electron optical system on the electron source side.
In the electron beam exposure apparatus, the illumination electron optical system comprises a plurality of electron lenses disposed in an optical axis direction, and the adjustment unit adjusts the focal length of the illumination electron optical system while fixing the focal point position of the illumination electron optical system on the electron source side, by changing focal lengths of at least two of the plurality of electron lenses.
The electron beam exposure apparatus further comprises an axis correction unit for correcting position deviations of the intermediate images to be projected onto the object to be exposed produced when the adjustment unit adjusts the focal length of the illumination electron optical system.
In the electron beam exposure apparatus, the axis correction unit corrects the position deviations of the intermediate images of the electron source to be projected onto the object to be exposed by correcting positions of the plurality of intermediate images formed immediately below the plurality of elementary electron optical syst
Anderson Bruce
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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