Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement
Reexamination Certificate
2000-01-10
2001-04-17
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Including control feature responsive to a test or measurement
C430S296000, C430S942000, C250S492220, C250S492300
Reexamination Certificate
active
06218060
ABSTRACT:
BACKGROUND ART
The present invention relates to an electron-beam lithography system or, more particularly, to a multicolumn electron-beam lithography system, having a plurality of electron-beam exposure systems, which offers an improved throughput.
Semiconductor integrated circuits now tend to have circuit elements thereof integrated to a higher degree due to advances in microprocessing technologies. The performance of the microprocessing technologies is becoming better. Above all, photolithography technology that is implemented in, for example, a conventional step-and-repeat photolithography system with demagnification, is expected, to reach its limits. Electron-beam lithography technology has the potential to take over from photolithography technology and become the new standard microprocessing technology. Electron-beam lithography technology is drawing attention as a next-generation lithography technology.
TECHNICAL FIELD
FIG. 1
shows the configuration of an electron-beam lithography system. There are shown a processor
1
, a magnetic disk
2
, and a magnetic tape drive
3
. These units are interconnected by a bus
4
, and connected to a data memory
6
and a stage control circuit
7
via an interface circuit
5
over the bus
4
.
A housing (column)
8
accommodates an electron gun
9
, a lens
10
, a blanking electrode
11
, a lens
12
, a feedback coil
13
, a sub deflector coil
14
, a lens
15
, a main deflector coil
16
, a stage
17
, and a sample
50
. The sample
50
is placed on the stage
17
. The stage
17
is controlled to be moved in x and Y directions according to an output signal of the stage control circuit
7
.
Moreover, data read from the data memory
6
is supplied to a pattern correction circuit
20
via a pattern generation circuit
19
. The pattern correction circuit
20
applies a blanking signal to the blanking electrode
11
via an amplifier
21
. Moreover, the pattern correction circuit
20
applies a signal to the coils
13
,
14
, and
16
via D/A converters (DAC)
22
,
24
, and
26
and amplifiers
23
,
25
, and
27
.
An electron beam radiated from the electron gun
9
is passed through the lens
10
, and transmitted or intercepted by the blanking electrode
11
. The electron beam is reshaped into a rectangular beam of parallel rays permitting a spot of 3 &mgr;m or less in diameter. The beam is then deflected by the feedback coil
13
, sub deflector coil
14
, and main deflector coil
16
. The beam is then passed through a projection lens
15
and converged on the surface of the sample. The areas over which the feedback coil
13
, sub deflector coil
14
, and main deflector coil
16
can deflect light get larger in that order. For ensuring a larger area in which light can be deflected, the number of windings of a coil must be increased. Response times required by the feedback coil
13
, sub deflector coil
14
, and main deflector coil
16
get longer in that order. That is to say, the settlement wait time required by the feedback coil
13
is the shortest. The settlement wait times required by the sub deflector coil
14
and main deflector
16
get longer in that order.
The above description is applied to a lithography method using a rectangular beam for exposure. There are various other methods including a block lithography method and a blanking aperture array lithography method. The basic configuration adaptable to the methods is identical to that shown in FIG.
1
.
FIG. 2
is an explanatory diagram concerning deflections achieved for exposure by a main deflector and sub deflector. As shown in
FIG. 2
, an exposure pattern to be drawn on one chip during exposure is divided into a plurality of portions M-
1
, M-
2
, etc. each of which is slightly narrower than a deflection range within which the sub deflector can deflect light. Exposure is carried out for drawing each portion. A magnitude of deflection u achieved by the main deflector is set to a fixed value permitting the main deflector to deflect an electron beam from the center O of the column to the center of a portion to be exposed. The portion of the pattern is then exposed while a magnitude of deflection v to be achieved by the sub deflector is being varied. When exposure of one portion is completed, the magnitude of deflection u to be achieved by the main deflector is changed to another fixed value permitting the main deflector to deflect the electron beam into the center of a portion to be exposed next. The portion is then exposed with the sub deflector as mentioned above. The data of the exposure pattern is therefore, as described later, composed of main deflector-related deflection data and sub deflector-related deflection data. The main deflector-related deflection data indicates the center of a portion of the exposure pattern. The sub deflector-related deflection data indicates a portion of the exposure pattern.
Electron-beam lithography systems are characterized by a resolution higher than that provided by photolithography systems but have a drawback that the throughput offered by the electron-beam lithography systems is lower than that offered by the photolithography systems. To improve the throughput, a plurality of columns may be included. An electron-beam lithography system having a plurality of columns is referred to as a multicolumn electron-beam lithography system.
FIG. 3
is a cutaway showing an example of structures for the multicolumn electron-beam lithography system. The multicolumn electron-beam lithography system may be realized in such a manner that columns each have a stage and expose different wafers. However, in this case, although the multicolumn electron-beam lithography system has a spatial advantage over the employment of a plurality of electron-beam lithography systems arranged mutually adjacently it cannot be said to have a great advantage over it. The multicolumn electron-beam lithography system can therefore be designed in such a manner that the distance between adjoining columns is made so short that the columns can concurrently expose one wafer so as to draw a pattern. In this case, an exposure time required for one wafer can be shortened. The present invention relates to this type of multicolumn electron-beam lithography system.
The electron-beam lithography system employs a high-performance data processing apparatus (computer) for processing abundant data of exposure patterns. For realizing a multicolumn electron-beam lithography system, one data processing apparatus should preferably be able to supply the same pattern data to each column. It is therefore not preferable to install a data processing apparatus for each column.
As shown in
FIG. 4
, numerous chips are defined in the form of a grid on a wafer. When the columns are used to expose chips concurrently, exposure can be achieved using the same pattern.
FIG. 4
relates to a configuration including four columns, wherein the center axes of the columns coincide with positions indicated with x on a wafer
50
. Reference numeral
51
denotes chips. Chips A are exposed using the first column, chips B are exposed using the second column, chips C are exposed using the third column, and chips D are exposed using the fourth column. During exposure, the wafer
50
placed on the stage is moved in order to align the center of each chip with the center axis of each column. Specifically, the wafer is moved so that the centers of the columns will follow trajectories indicated with dashed lines having arrows. When the left upper ones of the chips B, C, and D respectively are exposed, there is no chip A to be exposed by the first column, that is, the first column will expose no chip. This description will prove true when a deflection range of the main deflector within which the main deflector can deflect light is larger than one chip. When the deflection range of the main deflector is smaller than one chip, one chip is divided into a plurality of blocks. The stage is moved in order to align the centers of the columns with the centers of blocks. Moreover, for improving efficiency in exposure, while the stage
Komami Hideaki
Yasuda Hiroshi
Advantest Corporation
Christie Parker & Hale LLP
Young Christopher G.
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