Method of correcting alignment

Details Method of correcting alignment Method of correcting alignment

1999-02-24

2002-01-15

Picardat, Kevin M. (Department: 2823)

Semiconductor device manufacturing: process

With measuring or testing

C438S018000, C438S460000, C438S462000

Reexamination Certificate

active

06338971

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alignment correcting method for making a position alignment of patterns relative to each other in a horizontal direction when a plurality of patterns are formed in manufacturing a semiconductor device.
2. Description of the Background Art
Alignment will be discussed with reference to the conceptual view of
FIG. 52. A
semiconductor device comprises a plane
3
a
having patterns
1
a
and alignment marks
2
a
to
2
d,
and a plane
3
b
having patterns
1
b
and alignment marks
2
e
to
2
h.
The patterns
1
a
and
1
b
are formed on a wafer and made of a silicon compound, metal or the like. The alignment marks
2
a
to
2
d
are formed at the same time as the patterns
1
a.
The alignment marks
2
e
to
2
h
are formed at the same time as the patterns
1
b.
The term “alignment” is meant to define the operation of relatively aligning the position of the patterns
1
a
in the plane
3
a
for use in the next step with the position of the existing patterns
1
b
in the plane
3
b,
for example.
In a process for manufacturing a semiconductor device, several major steps are performed to manufacture the semiconductor device. The major step termed herein means a group of steps for forming one pattern (e.g., a film-formation step for forming a film on a wafer, a resist coating step for coating with a resist, an exposure step, a development step, and an etching step for patterning a film).
FIG. 53
is a conceptual sectional view of a semiconductor device. The semiconductor device of
FIG. 53
is provided by performing seven major steps. Since one pattern is formed in each major step, the semiconductor device comprises seven patterns
301
to
307
formed finally in a stacked relation through seven major steps, respectively.
One of the steps which require alignment in one major step is an exposure step. In the exposure step, alignment is performed in practice to relatively align the positions of a reticle and a wafer with each other. Apparatuses for exposure and alignment include, for example, a step-type projection aligner (referred to hereinafter as a “stepper”).
FIG. 54
is a block diagram of a production system
10
for manufacturing a semiconductor device. The production system
10
comprises a production control system body
6
for controlling the manufacture of a semiconductor device and connected to a stepper
4
as mentioned above, an overlay checking device
5
, and other semiconductor manufacturing devices
7
through reference terminals
8
. The production control system body
6
may be connected to a plurality of steppers
4
and to a plurality of semiconductor manufacturing devices
7
such as a sputtering device and an etching device.
The production system
10
uses the semiconductor manufacturing devices
7
including the steppers
4
to form, for example, a plurality of semiconductor integrated circuits
21
on a wafer
20
. Lead frames, leads and packages are added to the semiconductor integrated circuits
21
in an assembly step for formation of semiconductor devices. The above-mentioned planes
3
a
and
3
b
of the semiconductor device correspond to, for example, layers of the semiconductor integrated circuits
21
.
The stepper
4
connected to the production control system body
6
has an alignment function for exposing the same wafer to a plurality of shots of light. Unfortunately, there arises a shear between the patterns aligned by the stepper
4
despite of the alignment. The shear is due to various causes such as a mechanical error of the stepper itself and a reticle manufacturing error. The stepper
4
is given a correction value for eliminating the shear (referred to hereinafter as a “stepper correction value”). On the other hand, the overlay checking device
5
detects the shear to calculate a correction value for eliminating the shear (referred to hereinafter as an “overlay checking correction value”). The detection of the shear in the overlay checking device
5
is termed “overlay checking.”
The production control system body
6
controls data on alignment (referred to hereinafter as “alignment data”) which are provided from the stepper
4
and the overlay checking device
5
. The alignment data include the overlay checking correction value, the stepper correction value, the type of a wafer (lot No., product No. and the like), the date and time when alignment was performed, the contents of processing, a production history and the like. The alignment data are stored in a database
6
b.
An alignment correction unit
6
a
is one of the functions of the production control system body
6
, and calculates the stepper correction value, for example, using the alignment data stored in the database
6
b.
The stepper correction value calculated includes a stepper correction value for a wafer component, and a stepper correction value for a shot component. The stepper correction value is applied to the stepper
4
.
FIG. 55
conceptually illustrates a structure of the stepper
4
. The wafer
20
to be exposed is placed on a wafer stage WST. A reticle
30
formed with a pattern image to be drawn on the wafer
20
is provided on a reticle stage RST. An illumination system ILS directs a light beam for exposure onto the reticle
20
on the reticle stage RST. The light beam for exposure passed through the reticle
30
is refracted by a lens system PL to form an image
34
on the wafer
20
. The stepper
4
is adapted to move the wafer stage WST in accordance with a value set by the stepper correction value for the wafer component to move the wafer
20
on the wafer stage WST. The stepper correction value for the wafer component includes information about offsets X and Y (base line), scalings X and Y, X-Y orthogonality, wafer rotation and the like. The stepper
4
is also adapted to change the image
34
directed from the illumination system ILS through the reticle
30
and the lens system PL onto the wafer
20
in accordance with the stepper correction value for the shot component. The stepper correction value for the shot component includes information about shot rotation, magnification and the like. As the reticle stage RST rotates about a central axis
32
in accordance with the setting of the shot rotation, the image
34
is rotated. The degree of magnification of the image
34
is changed depending on the difference in the degree to which the lens system PL and the like refract the light beam for exposure in accordance with the setting of the magnification.
The wafer processing controlled by the production control system body
6
will be discussed below. The alignment of the pattern
304
of
FIG. 53
will be taken as an example. The control of the production control system body
6
is performed according to the flowchart of FIG.
56
. First, the production control system body
6
transports a wafer
20
to be processed to the stepper
4
. When the wafer
20
to be processed reaches the stepper
4
, the alignment correction unit
6
a
calculates the stepper correction value (Step S
901
of FIG.
56
). The production control system body
6
sets the stepper correction value obtained by calculation for the stepper
4
reached by the wafer
20
to be processed (Step S
902
). The stepper
4
performs alignment (Step S
903
). After the completion of the alignment, the production control system body
6
registers the stepper correction value for the wafer to be processed in the database
6
b
to control the stepper correction value. After the processing in the stepper
4
, the production control system body
6
transports the wafer
20
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 overlay checking correction value for elimination of the detected shear (Step S
906
). Subsequently, the production control system body
6
collects overlay checki

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