Optics: measuring and testing – By alignment in lateral direction – With registration indicia
Reexamination Certificate
2000-08-28
2002-06-18
Evans, F. L. (Department: 2877)
Optics: measuring and testing
By alignment in lateral direction
With registration indicia
Reexamination Certificate
active
06407814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for correcting alignment to make a relative alignment between patterns in a plane direction for forming a plurality of patterns in manufacturing a semiconductor device, a method for manufacturing a semiconductor device and a semiconductor device.
2. Description of the Background Art
Now discussion will be presented on alignment with reference to a conceptional diagram of
FIG. 24. A
plane
3
a
has patterns la and alignment marks
2
a
to
2
d
. A plane
3
b
has patterns
1
b
and alignment marks
2
e
to
2
h
. The patterns
1
a
and
1
b
are formed on wafers and made of silicon compound, metal or the like. The alignment marks
2
a
to
2
d
are formed simultaneously with the patterns
1
a
. The alignment marks
2
e
to
2
h
are formed simultaneously with the patterns
1
b
. An operation to relatively align positions of two objects, such as the planes
3
a
and
3
b
, is referred to just as “Alignment”.
In a process for manufacturing a semiconductor device, several major steps are performed to manufacture the semiconductor device. The major step is a unit of a plurality of steps for forming a pattern (e.g., a film-formation step for forming a film on a wafer, a resist coating step for coating a resist, an exposure step, a developing step, an etching step for patterning a film and so on).
FIG. 25
is a conceptional section of a semiconductor device. The semiconductor device of
FIG. 25
is obtained through seven major steps, and patterns
301
to
307
are formed through the seven major steps, respectively.
The alignment is required in the exposure step. In the exposure step, actually, an alignment is performed to relatively align the positions of a reticle and a wafer. Among apparatuses for exposure and alignment is a step-type projection aligner (hereinafter, referred to as “stepper”).
FIG. 26
is a block diagram of a manufacturing system
10
for manufacturing a semiconductor device. This figure shows steppers
4
as mentioned above, overlay checking devices
5
, a production control system body
6
for performing a production control which includes an alignment correction unit
6
a
and a database
6
b
, semiconductor manufacturing devices
7
and reference terminals
8
connected to the production control system body
6
for making reference to the database
6
b
. In this system, there are a plurality of steppers
4
and semiconductor manufacturing devices such as a sputtering device and an etching device.
Among patterns which are aligned by the stepper
4
, there exist a shear despite of the alignment. This is due to a mechanical error of the stepper, a manufacture error of the reticle and so on. The stepper
4
is given a correction value for resolving the shear (hereinafter, referred to as “stepper correction value”). On the other hand, the overlay checking device
5
detects the shear and calculates a correction value for resolving the shear (hereinafter, referred to as “OCCV (overlay checking correction value)”).
The production control system body
6
controls data on alignment (hereinafter, referred to as “alignment data”). The alignment data include the OCCV, the step correction value, the type of wafer (lot No., product No. and the like), date of alignment, processing, production history and so on. The alignment data are stored in the database
6
b.
The alignment correction unit
6
a
is one of functions of the production control system body
6
and calculates the stepper correction value.
FIG. 27
illustrates a constitutional conception of the stepper
4
. In this figure shown are a wafer stage WST on which a wafer
20
is mounted, a reticle stage RST on which a reticle
30
is mounted, an illumination system ILS, a lens system PL, a stepper correction value for wafer component
22
and a stepper correction value for shot component
33
.
The stepper
4
receives the stepper correction value. The stepper correction value includes the stepper correction value for wafer component
22
and the stepper correction value for shot component
33
.
The stepper correction value for wafer component
22
is a value which is set to move the wafer. The stepper correction values for wafer component
22
includes stepper correction values for offsets X and Y (base line), scalings X and Y, X-Y orthogonality and wafer rotation. The wafer stage WST travels in accordance with the stepper correction values for wafer component
22
.
The stepper correction value for shot component
33
is a value which is set to change an image
34
projected on the wafer
20
from the illumination system ILS through the reticle
30
. The stepper correction values for shot component
33
include stepper correction values for shot rotation, magnification and the like. The image
34
varies with the stepper correction values for shot component
33
. In more detail, as to the shot rotation, the reticle stage RST rotates about a center axis
32
to rotate the image
34
. As to the magnification, the image
34
is enlarged or reduced by the lens system PL and the like.
The production control system body
6
processes the wafer as follows. Herein, an alignment of the plane
304
of
FIG. 25
will be taken as an example. The processing is performed according to a flowchart of FIG.
28
.
First, the production control system body
6
transports a wafer to be processed to the stepper
4
. When the wafer reaches the stepper
4
, the alignment correction unit
6
a
calculates the stepper correction value (Step S
901
of FIG.
28
).
The production control system body
6
sets the stepper correction value obtained by calculation to the stepper
4
(Step S
902
).
The stepper
4
performs an alignment (Step S
903
).
After completing the alignment, the production control system body
6
registers the stepper correction value in the database
6
b
to control the stepper correction value. Further, the wafer is transported from the stepper
4
to the overlay checking device
5
(Step S
904
),
The overlay checking device
5
detects a shear between the pattern
304
and the pattern
303
immediately therebelow with the positions of the alignment marks (Step S
905
). Further, the device
5
calculates the OCCV to resolve the detected shear (Step S
906
).
Subsequently, the production control system body
6
collects the OCCVs from the overlay checking devices
5
(Step S
907
). The system body
6
stores the collected OCCVs in the database
6
b
and controls them (Step S
908
).
Further, the production control system body
6
transports the wafer to be processed to the semiconductor manufacturing device
7
, as needed, where sputtering, etching and the like are performed.
Through the above steps, the production control system body
6
processes the wafer.
Next, a method for correcting alignment to calculate the stepper correction value in the background art will be discussed with reference to
FIGS. 29 and 30
. It is assumed that the stepper correction value set in the Step S
902
is +1 and the OCCV (which herein corresponds to the shear) detected in the Step S
906
is −2 in this alignment performed in the major step. Therefore, as shown in
FIG. 30
, if the stepper correction value is set at +3 in the alignment of the next major step, it is expected that the OCCV should be 0. The calculated difference between the stepper correction value and the OCCV is referred to as “true shear”. Specifically, this is expressed as,
true shear=stepper correction value−OCCV (1)
Shorter time lag between the present alignment and the next alignment causes smaller true shear.
As the time lag becomes longer, the true shear becomes larger. Then, the production control system body
6
controls a trend of the true shear in a major step as shown in
FIG. 31
, and the alignment correction unit
6
a
calculates a mean value of true shears at the time points P
1
to P
3
in the same major step as the stepper correction value to be set in the next major step tx.
Thus, in the background-art method for correcting ali
Evans F. L.
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Smith Zandra
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