Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
1998-12-22
2003-04-22
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S492100, C250S492220, C250S492300
Reexamination Certificate
active
06552353
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electron beam exposure and, more particularly, to a multi-electron beam exposure method and apparatus for drawing patterns using a plurality of electron beams to directly draw patterns on a wafer, or to expose a mask or reticle, and a device manufacturing method using the same.
2. Description of the Related Art
Electron beam exposure apparatuses include: a point beam type apparatus which uses a spot-like beam; a variable rectangular beam type apparatus which uses a beam variable in its size and having a rectangular section; and a stencil mask type apparatus which uses a stencil to form a beam having a desired sectional shape.
The point beam type electron beam exposure apparatus is exclusively used for research and development purposes because of low throughput. The variable rectangular beam type electron beam exposure apparatus has a throughput higher than that of the point beam type apparatus by one to two orders, though the problem of throughput is still serious in exposing a pattern in which fine patterns having a size of about 0.1 &mgr;m are highly integrated. The stencil mask type electron beam exposure apparatus uses a stencil mask having a portion corresponding to a variable rectangular aperture in which a plurality of repeated pattern through holes are formed. The stencil mask type electron beam exposure apparatus can advantageously form repeated patterns by exposure. If a semiconductor circuit needs so many transfer patterns that they cannot be formed in one stencil mask, a plurality of stencil masks must be prepared and used one by one. The time for exchanging the masks is required, resulting in a large decrease in throughput.
An apparatus for solving this problem is a multi-electron beam exposure apparatus that irradiates a sample surface with a plurality of electron beams along designed coordinates, deflects the electron beams along the designed coordinates to scan the sample surface, and at the same time, independently turns on/off the electron beams in correspondence with the pattern to be drawn, thereby drawing a pattern. The multi-electron beam exposure apparatus can draw an arbitrary pattern without using any stencil mask, so the throughput can be increased.
FIG. 17
shows the schematic arrangement of a multi-electron beam exposure apparatus. Reference numerals
501
a
,
501
b
, and
501
c
denote electron guns capable of independently turning on/off electron beams;
502
, a reduction electron optical system for reducing and projecting the plurality of electron beams from the electron guns
501
a
,
501
b
, and
501
c
on a wafer
503
; and
504
, a deflector for deflecting the electron beams reduced and projected on the wafer
503
.
The electron beams from the electron guns
501
a
,
501
b
, and
501
c
are deflected by the same amount by the deflector
504
. With reference to the beam reference position, the positions of the respective electron beams are sequentially settled on the wafer and the beams are deflected in an array having an array interval defined by the minimum deflection width of the deflector
504
. The electron beams expose different element exposure areas in exposure patterns to be formed.
FIGS. 18
,
19
, and
20
show a state in which the electron beams from the electron guns
501
a
,
501
b
, and
501
c
expose the corresponding element exposure areas in exposure patters (P
1
, P
2
, P
3
) to be formed in accordance with the same array. While the positions of the respective beams are settled and shifted on the array at the same time in the order of (1, 1), (1, 2), . . . , (1, 16), (2, 1), (2, 2), . . . , (2, 16), (3, 1), each beam is turned on at a position where an exposure pattern (P
1
, P
2
, P
3
) to be formed is present to expose the corresponding element exposure area in the exposure pattern (P
1
, P
2
, P
3
) to be formed.
In the multi-electron beam exposure apparatus, however, since a plurality of electron beams are deflected by the same minimum deflection width to simultaneously draw patterns, a pattern having a fractional size, with which a given electron beam has a deflection width other than an integer multiple of the minimum deflection width, cannot be drawn. To draw this pattern, the minimum deflection width must be set to a minimum deflection width corresponding to the greatest common divisor of a fractional pattern and an integral pattern corresponding to the current minimum deflection width. In general, since the new minimum deflection width becomes smaller than the old minimum deflection width, the amount of data for drawing increases.
The above problem will be described in detail below with reference to
FIGS. 17
to
20
. If all the exposure patterns P
1
, P
2
, and P
3
to be formed are based on the design rule of 100 nm, the minimum deflection width is set to 25 nm, and a 100-nm pattern is drawn by scanning each electron beam four times. If only the pattern P
3
is based on the design rule of 180 nm, the minimum deflection width is set to the greatest common divisor, 20 nm, of 100 nm and 80 nm. Assume that the element exposure area to be exposed by each electron beam is 3.6×3.6 (&mgr;m
2
). In this case, if the minimum deflection amount is 25 nm, the number of times of settling the position of each electron beam in exposing the element exposure area is 20,736. If the minimum deflection width is 20 nm, this number is 32,400. That is, in the presence of a fractional pattern, the number of times of settling increases about 1.5 times, and the amount of data for drawing also increases about 1.5 times.
When only the pattern P
3
is based on the design rule of 180 nm, in practice, a pattern having a line width of 180 nm may be approximately drawn by scanning an electron beam seven times without changing the minimum deflecting width from 25 nm. In this case, however, the drawing precision decreases.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems in the prior art, and has as its object to provide a multi-electron beam exposure method and apparatus which can suppress a decrease in throughput even in the presence of a fractional pattern in drawing patterns. It is another object of the present invention to provide a device manufacturing method capable of manufacturing a device with a precision higher than that in the prior art by using the multi-electron beam exposure method and apparatus.
In order to achieve the above objects, according to a preferable aspect of the present invention, there is provided a multi-electron beam exposure method of simultaneously drawing in a plurality of areas of a surface to be exposed by using a plurality of electron beams, comprising classifying drawing patterns into a plurality of groups in accordance with design rules, and drawing while changing a minimum deflection width of each electron beam in units of groups.
Preferably, drawing is sequentially performed in the respective areas of the plurality of groups. In addition, the diameter of each electron beam or the settling time therefor is changed in accordance with switching of the minimum deflection width.
According to another preferable aspect of the present invention, there is provided a multi-electron beam exposure method of deflecting a plurality of electron beams onto a surface to be exposed of an object with a minimum deflection width as a unit on the basis of drawing data, independently controlling irradiation of each electron beam for each deflecting operation, and drawing a pattern in an element exposure area in units of electron beams, thereby drawing in a subfield consisting of the plurality of element exposure areas and sequentially drawing in a plurality of subfields, comprising the step of classifying pattern groups in the drawing data into a plurality of groups on the basis of design rules, and determining an optimal minimum deflection width for each group in drawing each pattern group, the first dividing step of dividing the drawing data in units of the subfields, the second dividing step of di
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee John R.
Vanore David A.
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