Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-06-23
2003-11-25
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S492100, C250S492200, C250S492210, C430S005000, C430S030000, C430S322000, C430S396000, C378S034000, C378S035000
Reexamination Certificate
active
06653644
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pattern exposure method and apparatus for projecting a circuit pattern on a circuit member by a charged particle beam passing through a pattern exposure mask, and a method and system for fabricating a semiconductor integrated circuit by utilizing the pattern exposure method and apparatus. The present invention also relates to a pattern exposure mask used for exposure of a circuit pattern of the integrated circuit, a method for forming the pattern exposure mask, and an integrated circuit having a layer/film patterned by the exposure.
Recently, an integrated circuit such as an LSI (large scale integrated circuit) is widely utilized in various fields, and therefore, an increased integration density and an elevated productivity are strongly demanded. At present, a means for forming a circuit pattern in the integrated circuit includes an optical printing and a direct drawing using an electron beam. The resolution of the optical printing is not so high as that of the electron beam drawing, but the productivity of the electron beam drawing is not so high as that of the optical printing.
In general, in the optical printing, a circuit pattern is projected by a transmission light passing through a pattern exposure mask. In the electron beam drawing, on the other hand, an electron beam is magnetically deflected and scanned to directly draw the circuit pattern. At the present, however, there is a technology for causing the electron beam to pass through the pattern exposure mask to project the circuit pattern.
However, in the optical printing using the pattern exposure mask, the circuit pattern is projected by only the transmission light. However, in the electron beam projection using the pattern exposure mask, not only the circuit pattern is projected by a transmission electron beam, but also a background exposure is caused because of a scattering beam.
In this case, since the exposure strength of the circuit pattern by the transmission electron beam is intensified by the background exposure caused by the scattering beam, the radiation strength of the electron beam can be reduced.
Now, one prior art example of the above mentioned pattern printing system will be described with reference to
FIGS. 9
to
12
B.
FIG. 9
is a diagrammatic view of an essential part of an electron beam projection apparatus.
FIG. 10A
is a diagrammatic plan view showing a structure of a pattern exposure mask, and
FIG. 10B
is a diagrammatic sectional view of the pattern exposure mask.
FIGS. 11A
,
11
B,
12
A and
12
B illustrate the order of the pattern printing method.
FIGS. 11A and 12A
are diagrammatic views schematically showing the relation between the pattern exposure mask and the electron beam that is a charge particle beam.
FIGS. 11B and 12B
are diagrams showing the exposure strength on the circuit member.
The shown electron beam projection apparatus, generally designated with the reference number
100
, has a pattern exposure mask
200
which is a replaceable parts. The pattern exposure mask
200
has a plurality of exposure regions
201
. Specifically, as shown in
FIG. 10A
, the pattern exposure mask
200
is formed in the form of a square plate, and a number of square exposure regions
201
are arranged in the form of matrix having a number of rows and a number of columns. The square exposure regions
201
are separated from one another by a boundary region
202
.
Furthermore, since the pattern exposure mask
200
is so configured to project the circuit pattern of one circuit member by one pattern exposure mask, the circuit pattern of the one circuit member is divided into a plurality of circuit sub-patterns, and the plurality of square exposure regions
201
in the one pattern exposure mask
200
correspond to the plurality of circuit sub-patterns, respectively. Therefore, each of the plurality of square exposure regions
201
in the one pattern exposure mask
200
includes a plurality of beam transmission parts
203
and a plurality of beam scattering parts
204
. As shown in
FIG. 11A
, the beam transmission parts
203
are formed of through-holes formed in the pattern exposure mask
200
formed of silicon, and therefore, correspond to a shape of a portion to be exposed. The beam scattering parts
204
and the boundary region
202
are the remaining parts of the pattern exposure mask
200
excluding the beam transmission parts
203
, and therefore, correspond to a shape of a portion that should not be exposed.
The pattern exposure mask
200
is formed of an SOI (silicon on insulator) substrate which is a multi-layer substrate, and therefore, one layer remains on the boundary region
202
as a reinforcing support
205
. The pattern exposure mask
200
having the above mentioned structure is removably fitted on a predetermined place in the electron beam projection apparatus
100
.
This electron beam projection apparatus
100
includes an electron gun
101
as a beam irradiator for irradiating the electron beam (as the charged particle beam) onto the pattern exposure mask
200
. At an opposite side of the pattern exposure mask
200
, a holder stage
102
is provided as a member holding means for holding a silicon wafer
103
which is a circuit member to be exposed.
In the way of the path passing from the electron gun
101
through the pattern exposure mask
200
to the silicon wafer
103
, various electron optical systems
104
and
1054
and an aperture
106
are located so as to adjust the focusing and the reduction of an image of the electron beam projected onto the silicon wafer
103
.
In the electron beam projection apparatus
100
, furthermore, an irradiating and scanning means. (not shown) is constituted of a displacement mechanism (not shown) for vertically and horizontally displacing the electron gun
101
, and a scanning mechanism (not shown) for vertically and horizontally deflecting the electron beam irradiated from the electron gun
101
onto the pattern exposure mask
200
. By action of this irradiating and scanning means, the electron beam from the electron gun
101
is irradiated for each of the exposure regions
201
in the pattern exposure mask
200
, region by region in order.
Similarly, an irradiation adjusting means (not shown) is constituted of a displacement mechanism (not shown) for vertically and horizontally displacing the holder stage
102
holding the silicon wafer
103
, and a scanning mechanism (not shown) for vertically and horizontally deflecting the electron beam from passing through the pattern exposure mask
200
to be irradiated onto the silicon wafer
103
. By action of this irradiation adjusting means, a corresponding number of irradiation regions of the electron beam passing through the plurality of exposure regions
201
in the pattern exposure mask
200
is located closely to one another in order on a surface of the silicon wafer
103
held on the holder stage
102
, with no unexposed region corresponding to the boundary region
202
being interposed between the irradiation regions.
Thus, the electron beam projection apparatus
100
having the above mentioned features, a resist film formed on the silicon wafer
103
is exposed by the electron beam in accordance with the circuit pattern of the pattern exposure mask
200
. In this case, the electron beam from the electron gun
101
is irradiated onto each of the plurality of exposure regions
210
in the pattern exposure mask
200
, one by one, in the order, by action of the irradiation scan means.
Simultaneously, the irradiation regions of the electron beam having passed through the respective exposure regions
201
in the pattern exposure mask
200
are located closely to one another on the surface of the silicon wafer held on the holder stage
102
, with no unexposed region corresponding to the boundary region
202
, by action of the irradiation adjusting means.
Accordingly, as shown in
FIGS. 11A
,
11
B,
12
A and
12
B, the exposure regions
201
are located in the pattern exposure mask
200
with the boundary region
202
being between
Lee John R.
NEC Electronics Corporation
Scully Scott Murphy & Presser
Vanore David A.
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